Efficient photosensitized degradation of 4-chlorophenol over immobilized aluminum tetrasulfophthalocyanine in the presence of hydrogen peroxide

Metal-Free Organic Optoelectronic Molecule as a Highly Efficient Photocatalyst for the Degradation of Organic Pollutants

With the increasing consumption of natural resources, photocatalysis converting solar energy to chemical energy has attracted extensive attention of researchers owing to the advantages of developing energy-saving and environmentally benign processes. In this work, a facile and simple method was developed to synthesize a metal-free organic optoelectronic molecule (denoted as DPPRD), which is composed of a central diketopyrrolopyrrole moiety and two terminal units of a rhodanine (RD) moiety. This is a first green strategy toward the synthesis of DPPRD. Because of good thermal stability, narrow band gap, and excellent visible light absorption of solar spectrum, DPPRD exhibited to be an efficient and chemically stable photocatalyst for visible light degradation of organic pollutants such as bisphenol A (BPA) and methyl orange (MO) in aqueous solution. The control experiments with different types of radical scavengers implied that the hole (h⁺) and hydroxyl radicals (^•OH) were the key reactive species during the photodegradation processes. The photodegradation pathways of BPA and MO were thus proposed based on the identified intermediates. This improved method for DPPRD synthesis is expected to widen its applications to industrial production, whereas its excellent visible light photocatalytic activity would be utilized potentially in the field of environmental and industrial applications.

Hollow and sulfonated microporous organic polymers: versatile platforms for non-covalent fixation of molecular photocatalysts

Sulfonated hollow microporous organic polymers showed excellent heterogenization ability towards various cationic photocatalysts through ionic interaction.

Two luminescent metal–organic frameworks with multifunctional properties for nitroaromatic compounds sensing and photocatalysis

Two luminescent MOFs were employed as multifunctional materials for selectively sensing of nitroaromatic compounds and photodegradation of RhB.

An efficient dye-sensitized BiOCl photocatalyst for air and water purification under visible light irradiation

A photosensitized BiOCl catalyst was found to be effective for photocatalytic water purification and air remediation under visible light irradiation (λ > 420 nm). Prepared by a solvothermal method, the BiOCl crystals possessed a 3D hierarchical spherical structure with the highly active facets exposed. When sensitized by Rhodamine B (RhB), the photocatalyst system was more active than N-doped TiO2 for breaking down 4-chlorophenol (4-CP, 200 ppm) and nitric monoxide (NO, 500 ppb). The high activity could be attributed to the hierarchical structure (supplying feasible reaction tunnels for adsorption and transition of reactants or products) and the efficient exposure of the {001} facets. The former provides an enriched oxygen atom density that promotes adsorption of cationic dye RhB, and creates an oxygen vacancy state. The HO˙ and ˙O2(-) radicals produced from the injected electrons from the excited dye molecule (RhB*) into the conduction band of BiOCl were responsible for the excellent photocatalytic performance of the RhB-BiOCl system.

Mesopolymer modified with palladium phthalocyaninesulfonate as a versatile photocatalyst for phenol and bisphenol A degradation under visible light irradiation

A novel versatile photocatalyst, FDU-PdPcS, was prepared by immobilizing palladium phthalocyaninesulfonate (PdPcS) onto the FDU-15 mesopolymer via multi-step chemical modification processes involving chloromethylation of the FDU-15 mesopolymer first with chloromethyl methyl ether, a subsequent amination reaction with ethylenediamine, and finally modification with palladium phthalocyaninesulfonate via ionic interaction. The obtained FDU-PdPcS photocatalyst was characterized by the X-ray diffraction (XRD), UV-Vis spectrosopy and inductively coupled plasma (ICP) techniques. This photocatalyst not only affords a high dispersion of monomeric PdPcS molecules, which may further be stabilized by the pi-electron of benzene rings of FDU-15, but also provides a number of diamino groups inside the mesopores, which could be advantageous for the photodegradation of phenolic pollutants. In photodegradation studies of phenolic pollutants, the FDU-PdPcS catalyst exhibited excellent visible light photocatalytic activity and reusability. The photodegradation products of phenol and bisphenol A were investigated by the gas chromatoghraphy-mass spectrometry (GC-MS) technique. The results showed that the photodegradation products were composed of carboxylic acids and CO2. Isopropanol, sodium azide and benzoquinone were used as hydroxyl radical (OH*), singlet oxygen (1O2) and superoxide radical (O2*-) scavengers, respectively. The results suggested that 1O2 and O2*- were the prominent active species during the photodegradation process. A possible mechanism for the photodegradation of phenol was also discussed.

Poly(amidoamine) dendrimer-grafted porous hollow silica nanoparticles for enhanced intracellular photodynamic therapy

We report a novel photodynamic therapy (PDT) drug-carrier system, whereby third-generation (G3) polyamidoamine (PAMAM) was successfully grafted to the surface of porous hollow silica nanoparticles (PHSNPs), followed by the attachment of gluconic acid (GA) for surface charge tuning. The composite G3-PAMAM-grafted PHSNPs (denoted as G3-PHSNPs) with a diameter range of 100-200 nm and about 30 nm sized shell thickness retain bimodal pore structures (e.g. inner voids and porous structure of the shells) and PAMAM-functionalized outer layer with a large number of amino groups, allowing high loading efficacy of aluminum phthalocyanine tetrasulfonate (AlPcS4) and its effective release to target tissue. The GA-induced G3-PHSNPs were evidenced to be able to favorably cross tumor cell walls and enter into the cell interior. The generation of singlet oxygen ((1)O2) from AlPcS4-GA-G3-PHSNPs under visible light excitation was detected by the in situ electron spin resonance measurements and the oxidative reaction between the generated (1)O2 and a chemical probe. In vitro cellular experiments showed that the photosensitive GA-G3-PHSNPs exhibited a good biocompatibility in the dark and a higher killing efficacy against MCF-7 tumor cells upon irradiation as compared with free AlPcS4, which implies that the preformed photosensitive drug-carrier system might be potentially applicable in PDT.

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.

Mechanism investigation of visible light-induced degradation in a heterogeneous TiO2/eosin Y/rhodamine B system

Visible light-induced degradation of rhodamine B (RhB) and eosin Y (EO) in a heterogeneous TiO(2) P-25/EO/RhB system was investigated in the present work. The results showed that the photodegradation of RhB is enhanced significantly when EO is introduced into the P-25/RhB system. Under optimal conditions (50 mg P-25, 20 mg L(-1) EO), RhB (4 mg L(-1)) almost decomposed completely after 35 min of visible light irradiation, though EO was photodegraded simultaneously. The possible photodegradation mechanism was studied by the examination of active species HO*, O(2)(*-) anions, or dye radical cations through adding their scavengers such as methanol, t-butanol, benzoquinone, EDTA, and the I(-) anion. In addition, the electron paramagnetic resonance (EPR) spin trapping technique was also used to monitor the active oxygen species formed in the photocatalytic process. Combined with the contrastive experiments under different atmospheres (N(2)-purged or air) and in different systems, it can be deduced that dissolved O(2) plays a crucial role in dye photodegradation and the O(2)(*-) anion is possibly the major active oxygen species. The low degradation rate with the introduction of EDTA or I(-) indicated that dye radical cations also play a part in photodegradation. Furthermore, except for the dye-sensitized photodegradation on the P-25 surface, reaction in bulk solution also occurs in this system, leading to effective photodegradation of RhB.

Adsorption of phenol, p-chlorophenol and p-nitrophenol onto functional chitosan

Functional chitosan, chemically modified by salicylaldehyde (CS-SA), beta-cyclodextrin (CS-CD), and a cross-linked beta-cyclodextrin polymer (EPI-CD) were prepared as adsorbents to remove phenol, p-nitrophenol and p-chlorophenol from aqueous solution. Langmuir and Freundlich models were applied to describe the adsorption isotherm of phenols, and adsorption parameters were evaluated. Functional chitosan displayed outstanding adsorption ability for phenols. To our surprise, CS-CD exhibited specific adsorption ability for p-chlorophenol. The possible adsorption interaction was discussed. Effects of pH and KCl on the adsorption suggested that the adsorption of phenols was predominated by hydrogen bonding, hydrophobic interaction and pi-pi interaction not electrostatic interaction. Effect of temperature indicated that the low temperature was favorable for the adsorption of phenols. Separation of phenols and adsorbent regeneration were carried out by simple washing with ethanol and filtrating.