Copper(II) phthalocyanine tetrasulfonate sensitized nanocrystalline titania photocatalyst: Synthesis in situ and photocatalysis under visible light

Advances in photocatalytic degradation of organic pollutants in wastewaters: harnessing the power of phthalocyanines and phthalocyanine-containing materials

Access to clean water is increasingly challenging worldwide due to human activities and climate change. Wastewater treatment and utilization offer a promising solution by reducing the reliance on pure underground water. However, it is crucial to develop efficient and sustainable methods for wastewater purification. Among the emerging wastewater treatment strategies, photocatalysis has gained significant attention for decomposing organic pollutants in water, especially when combined with sunlight and a recoverable photocatalyst. Heterogeneous photocatalysts have distinct advantages, as they can be recovered and reused without significant loss of activity over multiple cycles. Phthalocyanine dyes, with their exceptional photophysical properties, are particularly valuable for homogeneous and heterogeneous photocatalysis. By immobilizing these photosensitizers in various supports, hybrid materials extend their light absorption into the visible spectrum, complementing most supports' limited UV light absorption. The novelty and research importance of this review stems from its discussion of the multifaceted approach to treating contaminated wastewater with phthalocyanines and materials containing phthalocyanines. It highlights key aspects of each study, including photocatalytic efficiency, recyclability characteristics, investigation of the generation of oxygen species responsible for degradation, identification of the major degradation byproducts for each pollutant, and others. Moreover, the review includes tables that illustrate and compare the various phthalocyanines and supporting materials employed in each study for pollutant degradation. Additionally, almost all photocatalysts mentioned in this review could degrade at least 5% of the pollutant, and more than 50 photocatalysts showed photocatalytic rates above 50%. When immobilized in some support, the synergistic effect of the phthalocyanine was visible in the photocatalytic rate of the studied pollutant. However, when performing these types of works, it is necessary to understand the degradation products of each pollutant and their relative toxicities. Along with this, recyclability and stability studies are also necessary. Despite the good results presented in this review, some of the works lack those studies. Moreover, none of the works mentions any study in wastewater.

Nanocomposites of Titanium Dioxide and Peripherally Substituted Phthalocyanines for the Photocatalytic Degradation of Sulfamethoxazole

Phthalocyanines (Pcs) are often used in photosensitization of titanium(IV) oxide, a commonly employed photocatalyst, as such an approach holds the promise of obtaining highly stable and efficient visible light-harvesting materials. Herein, we report on the preparation, characterization and photoactivity of a series of composites based on TiO₂ and peripherally modified metallophthalocyanines: either tetrasulfonated or 4,4',4'',4'''-tetraazaphthalocyanines, with either copper(II), nickel(II) or zinc(II) as the central metal ion. Physicochemical characterization was performed using UV-Vis diffuse reflectance spectroscopy, hydrodynamic particle-size analysis, surface-area analysis using N₂ adsorption-desorption measurements and thermogravimetry combined with differential scanning calorimetry. The band-gap energy values were lower for the composites with peripherally modified phthalocyanines than for the commercial TiO₂ P25 or the unsubstituted zinc(II) phthalocyanine-grafted TiO₂. TG-DSC results confirmed that the chemical deposition, used for the preparation of Pc/TiO₂ composites, is a simple and efficient method for TiO₂ surface modification, as all the Pc load was successfully grafted on TiO₂. The photocatalytic potential of the Pc/TiO₂ materials was assessed in the photocatalytic removal of sulfamethoxazole-a commonly used antibacterial drug of emerging ecological concern. To compare the activity of the materials in different conditions, photodegradation tests were conducted both in water and in an organic medium.

Highly effective ruthenium-doped TiO2nanoparticles photocatalyst for visible-light-driven photocatalytic hydrogen production

This paper reports the synthesis of bare TiO₂and various molar concentrations of ruthenium (Ru)-doped TiO₂nanoparticles by the precipitation method.

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Molecular aggregation phenomena of a highly water-soluble, metal-free phthalocyanine, H[Formula: see text]Pc, and its copper complex, Cu(Pc); where Pc denotes tetrakis{(2[Formula: see text],6[Formula: see text]-dimethyl-4[Formula: see text]-sulfonic acid)phenoxy}phthalocyaninate) in water, ethanol, and their mixed solvent systems have been investigated by spectroscopic approach In both aqueous and ethanolic solutions, H[Formula: see text]Pc molecules aggregate in a slipped-cofacial manner, although very weakly in ethanol. On the other hand, Cu(Pc) molecules aggregate in a cofacial manner in water while aligning in a slipped-cofacial manner in ethanol. Magnetic circular dichroism spectroscopy was undertaken to investigate aggregation behaviors of Cu(Pc) in water and ethanol. Presence of 4-phenylpyridine in ethanol effectively inhibited aggregation of Cu(Pc) molecules, although little affected the spectra of the monomers. In a mixed solvent system, where water/ethanol [Formula: see text] 10/90 (v/v), Cu(Pc) is free from aggregation up to almost 10[Formula: see text] M. Driving forces of this molecular aggregation are discussed on the basis of [Formula: see text]–[Formula: see text] interaction and coordination chemistry involving copper ions.

Fabrication and Functionalization of Inorganic Materials Using Amphiphilic Molecules

In this review, the synthesis of inorganic materials with various properties using amphiphilic molecules is examined. Amphiphilic molecules are used for the formation of highly ordered mesostructures and the surface modification. Two examples of the mesostructures are crystalline mesoporous titania (TiO₂) and the novel visible light responsive mesostuructured titania modified with dye in the pores, which can be fabricated using the molecular self-assemblies of amphiphiles as templates. Surface modification using amphiphilic molecules enables the construction of self-assembled arrays of silica particles and the preparation of a film that can control adsorption/desorption behavior of bovine serum albumin (BSA) by light irradiation.

The effect of ionic Co presence on the structural, optical and photocatalytic properties of modified cobalt–titanate nanotubes

With the aim of producing materials with enhanced optical and photocatalytic properties, titanate nanotubes (TNTs) modified by cobalt doping (Co-TNT) and by Na⁺ → Co ion-exchange (TNT/Co) were successfully prepared by a hydrothermal method.

Iron phthalocyanine modified mesoporous titania nanoparticles for photocatalytic activity and CO2 capture applications

An iron(II)phthalocyanine (Fepc) modified mesoporous titania (Fepc-TiO2) nanocatalyst with a specific surface area of 215 m(2) g(-1) has been synthesized by a hydrothermal method. Fepc-TiO2 degrades one of the highly toxic chemical warfare agents, sulfur mustard (SM), photocatalytically under sunlight with an exposure time of as low as 70 min. Furthermore, the mesoporous Fepc-TiO2 also captured 2.1 mmol g(-1) of CO2 at 273 K and 1 atm.

A novel Ru/TiO2 hybrid nanocomposite catalyzed photoreduction of CO2 to methanol under visible light

A novel in situ synthesized Ru(bpy)3/TiO2 hybrid nanocomposite is developed for the photoreduction of CO2 into methanol under visible light irradiation. The prepared composite was characterized by means of SEM, TEM, XRD, DT-TGA, XPS, UV-Vis and FT-IR techniques. The photocatalytic activity of the synthesized hybrid catalyst was tested for the photoreduction of CO2 under visible light using triethylamine as a sacrificial donor. The methanol yield for the Ru(bpy)3/TiO2 hybrid nanocomposite was found to be 1876 μmol g(-1) cat (ϕMeOH 0.024 mol Einstein(-1)) that was much higher in comparison with the in situ synthesized TiO2, 828 μmol g(-1) cat (ϕMeOH 0.010 mol Einstein(-1)) and the homogeneous Ru(bpy)3Cl2 complex, 385 μmol g(-1) cat (ϕMeOH 0.005 mol Einstein(-1)).

Bismuth and chromium co-doped strontium titanates and their photocatalytic properties under visible light irradiation

Bi/Cr were co-doped into SrTiO₃viatwo synthetic routes. Unlike Cr, Bi does not significantly contribute to the electronic structure near Fermi level.

Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers--spectroscopic investigations

The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

Synthesis, spectral and electrochemical properties of a novel phosphorous(V)-phthalocyanine

A novel phosphorous(V)-phthalocyanine, [ P ( tppc )( OH )( O )], where tppc denotes tetrakis{(2′,6′-dimethyl)phenoxy}phthalocyaninate, has been synthesized and its spectral properties in non-aqueous and aqueous media have been investigated. This compound has been found free from aggregation in EtOH whereas forms J-aggregates in CH 2 Cl 2 and acetonitrile, suggesting the presence of chemical interaction between the axial ligand and the surrounding solvent molecules. The most intense absorption band (Q-band) appears at 683 nm in EtOH , however, reaction with CF 3 COOH has given rise to a large red shift of the Q-band without lowering of its C 4 symmetry (evidenced by magnetic circular dichroism spectroscopy), indicating protonation at the axial site. Its fluorescence quantum yield has been determined (0.49 in EtOH ) and has been found much higher than those of the known Sb V or As V derivatives by more than one order of magnitude. The first reduction potential has been determined by cyclic voltammetry (-1.09 V vs. ferrocenium+/ferrocene) in CH 2 Cl 2. It is noteworthy that the Q-band maximum wavelength and the first reduction potential values are normal for conventional phthalocyanines despite the presence of pnictogen(V) in the cavity of the macrocyclic ligand.

Spectrophotometric studies of visible light induced photocatalytic degradation of methyl orange using phthalocyanine-modified Fe-doped TiO2 nanocrystals

In this paper, preparation and visible light induced photocatalytic activity of phthalocyanine-modified Fe-doped TiO(2) nanocrystals (Pc/Fe-TiO(2)) with different Fe doping content (0, 0.05, 0.5 and 3.0 mol% Fe) as photocatalysts for the degradation of methyl orange have been reported. The study carried out using XRD, FT-IR, EDX, BET, DRS, UV-Vis, SEM and TEM techniques. Results revealed that modified TiO(2) nanocrystals possessed only the anatase phase with crystal sizes of about 10-23 nm and high surface areas of 2.8-37.3 m(2)/g. It can be seen phthalocyanine and Fe(3+) ion exist in photocatalysts based on analysis of FT-IR and EDX. The doping amount of Fe remarkably affects the activity of modified TiO(2) nanocrystals as catalysts. The 0.5 mol% Fe doping exhibited enhanced photocatalytic activity in this work. It was found that phthalocyanine and Fe induced a shift in the energy band gap to lower energies, which changes from 3.26 to 2.26 eV for pure TiO(2) and Pc/3% Fe-TiO(2) nanocrystals, respectively. Results of the degradation of methyl orange revealed that modified TiO(2) nanocrystals showed much more photocatalytic activity than pure TiO(2) under visible light which makes the applicability of TiO(2) photocatalysts even more versatile.

Hierarchical nanostructures of copper(II) phthalocyanine on electrospun TiO(2) nanofibers: controllable solvothermal-fabrication and enhanced visible photocatalytic properties

In the present work, 2,9,16,23-tetranitrophthalocyanine copper(II) (TNCuPc)/TiO(2) hierarchical nanostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric and differential thermal analysis (TG-DTA) were used to characterize the as-synthesized TNCuPc/TiO(2) hierarchical nanostructures. The results showed that the secondary TNCuPc nanostructures were not only successfully grown on the primary TiO(2) nanofibers substrates but also uniformly distributed without aggregation. By adjusting the solvothermal fabrication parameters, the TNCuPc nanowires or nanoflowers were facilely fabricated, and also the loading amounts of TNCuPc could be controlled on the TNCuPc/TiO(2) hierarchical nanostructural nanofibers. And, there might exist the interaction between TNCuPc and TiO(2). A possible mechanism for the formation of TNCuPc/TiO(2) hierarchical nanostructures was suggested. The photocatalytic studies revealed that the TNCuPc/TiO(2) hierarchical nanostructures exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TNCuPc or TiO(2) nanofibers under visible-light irradiation.

Sulphonated cobalt phthalocyanine-MCM-41: an active photocatalyst for degradation of 2,4-dichlorophenol

The photocatalytic activity of sulphonated cobalt phthalocyanine immobilized onto MCM-41 was investigated for decomposition of 2,4-dichlorophenol (2,4-DCP) in aqueous solutions. Immobilization of anion sulpho-cobalt phthalocyanine to the walls of MCM-41 was performed by pre-anchorage of 3-(aminopropyl)-triethoxysilane (APTES) onto MCM-41 via post-synthesis method. X-ray diffraction, nitrogen physisorption, diffuse reflectance spectroscopy, energy-dispersive X-ray and FT-IR methods were used to characterize the product. Photocatalytic efficiency of the prepared catalyst for degradation of 2,4-DCP was tested under illumination of UV-A and visible light. The results obtained reveal that the photocatalyst is very active in degradation of 2,4-DCP. The photodegradation process is completed within 3h using a dose of 0.6g/L of the catalyst under UV irradiation. The reactions follow a pseudo-first-order kinetics and the observed rate constant values change with 2,4-DCP concentrations. The reproducibility of the catalyst was tested. The reaction intermediates were identified by gas chromatoghraphy-mass spectrometry (GC-MS) technique.