Narrow Results

The monomeric and polymeric tetra-aminophthalocyane to, cobalt(II) species adsorbed onto graphite electrodes are active in electrocatalytic oxygen reduction. While the monomeric species is unstable, the polymerized species is an effective and stable reduction catalyst over a wide pH range. Both the two-electron reduction of oxygen to hydrogen peroxide and the four-electron reduction of oxygen to water are characterized by cyclic voltammetry, rotating disc and rotating ring-disc studies with appropriate theoretical analysis. Some mechanistic information is obtained. This is the first cobalt phthalocyanine species to provide a four-electron reduction pathway which exists over a wide pH range and is stable. The stability is associated with the polymerization since the monomeric species is not stable.

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [CPI]/[Cd(II)] two types of complex were formed: CdII(CPI) and (CdII)₂(CPI); an investigation of the solution properties and the mechanism of aggregation of (CdII)₂(CPI) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII(CPI) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell's sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 ± 0.026) × 10⁵ 1 mol⁻¹ cm⁻¹ and (1.820 ± 0.008) × 10⁻⁴ μg cm⁻² respectively.

Monomeric and polymeric iron phthalocyanine compounds were synthesized and their dielectric properties were measured in the frequency range from 100 Hz to 10 MHz between 25 and 200 °C. The dielectric constant and dielectric loss showed strong frequency and temperature dependences. Interestingly, large dielectric constants were observed around 100 °C for both monomers and polymers. A dielectric constant as high as 5000 at 110 Hz was observed for the iron phthalocyanine polymer. The origin of the large dielectric constant in metallophthalocyanines is discussed.

Polymer-bound cobalt(II) porphyrins were studied for their dioxygen—binding capacity. Tetra—aminoporphyrins were anchored on a divinylbenzene (DVB)-crosslinked chloromethyl polystyrene network. The crosslinked, solid polymers were swelled in chloroform and the swollen polymers were used for the entire studies. Ortho-, meta- and para-substituted porphyrin systems were developed by adjusting the bonding position with the help of suitably substituted aminoporphyrins. The products were characterized by chemical and spectroscopic methods. Cobalt(II) complexes of polymeric porphyrins were synthesized and characterized by electronic and ESR spectral methods. The spectra gave evidence for the systematic variation of electronic properties in ortho, meta and para compounds and for the dioxygen-binding capacity of cobalt complexes. These results are discussed.

In this review, free-base and metalloporphyrins, functionalized on meso-positions by quaternary pyridinium units, also referred to as cationic porphyrins, are presented. The article consists of five parts. In the first part free-base porphyrins are described, especially taking account on generation of singlet oxygen; next parts concern metalloporphyrins. The second and third parts deal with zinc and manganese porphyrins, respectively; in the fourth part copper, palladium, and platinum porphyrins are presented. In the fifth part, describing porphyrins with various metal ions an attention is paid to porphyrin metal-organic frameworks (MOFs) and metal-organic materials (MOMs) in which metalloporphyrins are immobilized; syntheses and characterization of obtained products are shown.

Current work is devoted to covalent immobilization of sulfonated derivatives of cobalt phthalocyanines “Merox catalysts” on the surfaces of polypropylene and polyethylene terephthalate. Their catalytic activity in reaction of mild oxidation of sulfur compounds to disulfides with oxygen of the air was studied. Anchoring of the catalyst on this polymer prevents its leaching and promotes its efficient recovering and recycling without significant loss of catalytic activity.

Mono or diamino phthalocyanines with A3B or crosswise ABAB substitution patterns have been synthesized and used as building blocks for the preparation of dimeric and polymeric phthalocyanines. For this, 4,5-di(dodecylsulfanyl) phthalonitrile was converted into 1,3-diimino-6,7-di-($n$-dodecylsulfanyl)-isoiminoindoline and then reacted with 6-nitro-1,3,3-trichloroisoindoline. The nitro functions on the resulting inseparable mixture of A3B and ABAB phthalocyanines were reduced into amines by Na₂S and the phthalocyanines could be chromatographically separated. Dimeric phthalocyanine was synthesized by the reaction of the mono-amino AB3 with sebacoyldichloride, and a poorly soluble linear polymeric material was obtained by reaction of the ABAB di-amino phthalocyanine with sebacoyl dichloride.

Photodynamic therapy (PDT) and photothermal therapy (PTT) are promising therapeutic methods for cancer treatment. However, both PDT and PTT have their own limitations. Thus, it is highly desirable to synthesize a single photosensitizer, which exhibits both PDT and PTT therapeutic performances. We have designed and synthesized a new porphyrin-based polymer (ZP-PT) by cross-linking fluoroporphyrins (ZnPor) and HS-terminated pentaerythritol tetra(3-mercaptopropionate) (PETMP). After being transformed into nanoparticles (ZP-PT NPs), they showed excellent water dispersity with the average size of about 100 nm. ZP-PT NPs could generate reactive oxygen species (ROS) and thermal energy under 635 nm laser irradiation. The singlet oxygen yield and the photothermal conversion efficiency (PCE) of ZP-PT NPs were calculated to be 0.46 and 27.07% respectively, which were apparently higher than that of ZnPor NPs. In addition, ZP-PT NPs exhibited higher colloidal stability and photostability than that of ZnPor NPs. All these results suggested that ZP-PT NPs had great potential in photodynamic and photothermal synergistic treatment of cancer.

Cadmium sulphide (CdS) nanocrystallites were prepared by sulphuration route with capping in polyethylene oxide (PEO) polymer matrix. It is found that PEO could provide a confined environment for particle nucleation and growth of CdS nanocrystallites. The scanning electron microscopy (SEM) with energy dispersive analysis by X-ray (EDAX) studies confirms the presence of CdS nanocrystallites in polymer matrix. X-ray diffraction (XRD) studies and transmission electron microscopy (TEM) selected area diffraction (SAD) patterns show that these crystallites have hexagonal structure. The TEM and UV-Visible absorption studies indicate uniform size distribution having size around 2.3 nm and band gap of 2.7 eV. X-ray photoelectron spectroscopy (XPS) studies reveal that core level energy positions of the Cd is shifted towards the lower binding energy and has similar chemical environment to that of bulk CdS.

A novel and shape-controlled synthesis method for uniformly-shaped poly(p-phenylenediamine) (PpPD) microparticles was developed using (NH₄)₂S₂O₈ (APS) as an oxidant. The results demonstrated that the morphologies of PpPD varied from nanofibers to nanospheres and nest-like microspheres by tuning the pH of solution. Tiny pH change leads to the significant change in product morphology. The structure of microspheres is similar to graphene which was first discovered. Further study showed that the PpPD nanofibers were dimer. The difference in the structure of PpPD nanofibers and nanospheres (microspheres) resulted in different solubility in water. The nanosized oligomer crystallites served as starting templates for the nucleation of PpPD nanofibers. Further growth of nanofibers was proceeded by the self-organization of phenazine units or their blocks located at the ends of the PpPD chains.

The electrochemical properties of poly sodium 4-styrenesulfonate intercalated graphite oxide (PSSGO) have been investigated in a 1 M H₂SO₄ electrolyte. We observed capacitor behavior at scan rate of 1–25 mV/s in a cyclic voltammetry. Specific capacitance obtained from galvanostatic charge and discharge measurements were 6 F/g to 102 F/g at 1 A/g to 0.1 A/g, respectively. The specific capacitance of PSSGO is relatively high compared to that of the precursor graphite oxide in which the specific capacitance was 11–20 F/g at 0.03 A/g. Capacitance retention was 73% after 3000 cycles, proving reliable cyclic stability up to 3000 cycles.

Amphiphilic polymer carriers (PEG–St–$R$) were prepared from cassava starch and their pH response was investigated. First, hydrophobic tapioca starch polymer (St–$R$) was prepared with octyl acyl as the hydrophobic group. The hydrophilic group polyethylene glycol (mPEG) was then introduced into the polymer by esterification to produce amphiphilic tapioca starch polymer (PEG–St–$R$). Its self-assembly behavior was characterized using fluorescent probes. The morphology of PEG–St–$R$ was investigated by transmission electron microscopy (TEM). Loading of the anti-cancer drug curcumin was used to assess the delivery and slow-release performance of the amphiphilic tapioca starch polymer. Cumulative drug release was explored at various pH conditions, with the greatest release from drug-loaded micelles being observed under acidic conditions and stable in a neutral environment. These results provide a theoretical basis for the preparation of pH-responsive nanomicelle carriers, and a platform for the preparation of novel amphiphilic starch-based polymers.

Devices such as solar and fuel cells have been studied for many decades and noticeable improvements have been achieved. This paper proposes a Micro Photosynthetic Power Cell (μPSC) as an alternative energy-harvesting device based on photosynthesis of blue-green algae. The effect of important biodesign parameters on the performance of the device, such as no-load performance and voltage–current (V–I) characteristics, were studied. Open-circuit voltage as high as 993 mV was measured while a peak power of 175.37 μW was obtained under an external load of 850 Ω. The proposed μPSC device could produce a power density of 36.23 μW/cm², voltage density of 80 mV/cm² and current density of 93.38 μA/cm² under test conditions.

Membrane technologies are essential for water treatment, bioprocessing and chemical manufacturing. Stimuli-responsive membranes respond to changes in feed conditions (e.g., temperature, pH) or external stimuli (e.g., magnetic field, light) with a change in performance parameters (permeability, selectivity). This enables new functionalities such as tunable performance, self-cleaning and smart-valve behavior. Polymer self-assembly is a crucial tool for manufacturing such membranes using scalable methods, enabling easier commercialization. This review surveys approaches to impart stimuli responsive behavior to membrane filters using polymer self-assembly.

Mono or diamino phthalocyanines with A3B or crosswise ABAB substitution patterns have been synthesized and used as building blocks for the preparation of dimeric and polymeric phthalocyanines. For this, 4,5-di(dodecylsulfanyl) phthalonitrile was converted into 1,3-diimino-6,7-di-(n-dodecylsulfanyl)-isoiminoindoline and then reacted with 6-nitro-1,3,3-trichloroisoindoline. The nitro functions on the resulting inseparable mixture of A3B and ABAB phthalocyanines were reduced into amines by Na₂S and the phthalocyanines could be chromatographically separated. Dimeric phthalocyanine was synthesized by the reaction of the mono-amino AB3 with sebacoyldichloride, and a poorly soluble linear polymeric material was obtained by reaction of the ABAB di-amino phthalocyanine with sebacoyl dichloride.