Surface chemistry and electrocatalytic behaviour of tetra-carboxy substituted iron, cobalt and manganese phthalocyanine monolayers on gold electrode

Highly improved photoreduction of carbon dioxide to methanol using cobalt phthalocyanine grafted to graphitic carbon nitride as photocatalyst under visible light irradiation

A substantially improved methanol yield was achieved from the photoreduction of carbon dioxide under visible light by using a hybrid photocatalyst consisting of molecular cobalt phthalocyanine tetracarboxylic acid (CoPc-COOH) complex immobilized to the organic semiconductor graphitic carbon nitride (g-C₃N₄) and triethylamine as sacrificial electron donor. The structural and morphological features of the hybrid photocatalyst determined by various techniques like FTIR, UV-Vis, Raman, XPS, TGA, BET etc. After 24 h of light irradiation, the methanol yield by using g-C₃N₄/CoPc-COOH photocatalyst (50 mg) was found to be 646.5 µmol g^-1cat or 12.9 mmol g^-1cat with conversion rate 538.75 µmol h^-1 g^-1cat. However, the use of homogeneous CoPc-COOH (6.5 µmol Co, equivalent to g-C₃N₄/CoPc-COOH) and g-C₃N₄ (50 mg) provided 88.5 μmol (1770 μmol g^-1cat) and 59.2 μmol (1184 μmol g^-1cat) yield of methanol, respectively under identical conditions. The improved photocatalytic efficiency of the hybrid was attributed to the binding ability of CoPc-COOH to CO₂ that provided the higher CO₂ concentration on the support. Further, the semiconductor support provided better electron mobility and charge separation with the integrated benefit of facile recovery and recycling of the material at the end of the reduction process.

Symmetrical and difunctional substituted cobalt phthalocyanines with benzoic acids fragments: Synthesis and catalytic activity

Difunctional and symmetric phthalonitriles were synthesized by nucleophilic substitution of brome and nitro-group in 4-bromo-5-nitro-phthalonitrile for residues 4-amino-, 4-hydroxyl- and 4-sulfanyl benzoic acid. Symmetrical and difunctional substituted cobalt phthalocyanines were obtained by template synthesis based on mentioned phthalonitriles. Their spectral properties and catalytic activity in aerobic oxidation of sodium [Formula: see text],[Formula: see text]-carbomoditiolate were investigated.

Simultaneous electrochemical detection of dopamine and epinephrine in the presence of ascorbic acid and uric acid using a AgNPs–penicillamine–Au electrode

A silver nanoparticle immobilized penicillamine self-assembled electrode, AgNPs–PCA–Au, can simultaneously sense dopamine, epinephrine, ascorbic acid and uric acid at neutral pH.

Electrochemical detection of adenine and guanine using a self-assembled copper(ii)–thiophenyl-azo-imidazole complex monolayer modified gold electrode

A self-assembled copper(ii)–thiophenyl-azo-imidazole complex monolayer modified gold electrode exhibits an excellent electrochemical sensing ability towards adenine and guanine at physiological pH.

Interactions between rotavirus and natural organic matter isolates with different physicochemical characteristics

Interaction forces between rotavirus and Suwanee River natural organic matter (SRNOM) or Colorado River NOM (CRNOM) were studied by atomic force microscopy (AFM) in NaCl solutions and at unadjusted pH (5.7-5.9). Compared to CRNOM, SRNOM has more aromatic carbon and phenolic/carboxylic functional groups. CRNOM is characterized with aliphatic structure and considerable presence of polysaccharide moieties rich in hydroxyl functional groups. Strong repulsive forces were observed between rotavirus and silica or mica or SRNOM. The interaction decay length derived from the approaching curves for these systems involving rotavirus in high ionic strength solution was significantly higher than the theoretical Debye length. While no adhesion was observed for rotavirus and SRNOM, attraction was observed between CRNOM and rotavirus during approach and adhesion during retraction. Moreover, these adhesion forces decreased with increasing ionic strength. Interactions due to ionic hydrogen bonding between deprotonated carboxyl groups on rotavirus and hydroxyl functional groups on CRNOM were suggested as the dominant interaction mechanisms between rotavirus and CRNOM.

Near-infrared fluorescent ribonuclease-A-encapsulated gold nanoclusters: preparation, characterization, cancer targeting and imaging

Ultra-small gold nanoclusters (AuNCs) have unique size-dependent optical, electrical and chemical properties. They have emerged as a new nanomaterial with broad applications in optoelectronics, catalysis, biosensing, and bioimaging. Several strategies have been exploited to prepare AuNCs of different "magic number" sizes, using different templates e.g. dendrimers, polyethyleneimines, peptides, and more recently, proteins. Notwithstanding, almost all bio-template-protected AuNCs reported so far exhibit fairly low fluorescence quantum yields (QYs), typically <5%, which is especially true for AuNCs prepared using the protein templates. In this paper, we report a facile, one-pot aqueous synthesis of highly fluorescent AuNCs using bovine pancreatic ribonuclease A (RNase-A) as the bio-template. The as-prepared AuNCs not only fluoresce strongly at the near-infrared (NIR) region (λ(em) = 682 nm), but also exhibit an elevated QY of ∼12%. Additionally, the RNase-A-encapsulated AuNC (RNase-A-AuNC) displays an exceptionally large Stokes shift of ∼210 nm as well as a single dominant fluorescence lifetime of ∼1.5 μs, about three orders of magnitude longer than biological autofluorescence. Furthermore, by coupling vitamin B(12) (VB(12)) to the RNase-A-AuNC, we develop a multifunctional nanoplatform that is suitable for simultaneous targeting and imaging of cancer at the cellular level using Caco-2 cell lines as an in vitro model. Since VB(12) has effective uptake pathways in the digestive system, this nanoplatform may have potential for targeted oral drug delivery in vivo.

Metallophthalocyanines and metalloporphyrins as electrocatalysts: a case of hydrogen peroxide and glucose detection

This review summarizes the applications of metallophthalocyanine (MPc) and metallo-porphyrin (MP) complexes as electrocatalysts immobilized onto various electrodes for the detection of hydrogen peroxide and glucose. The uses of MPc and MP complexes as electron mediators for the detection of glucose at glucose oxidase modified surfaces are discussed.

Applications of polymerized metal tetra-amino phthalocyanines towards hydrogen peroxide detection

This work reports the use of metallo tetra-amino phthalocyanines ( MTAPc, M = Co and Mn ) polymer thin films on gold and glassy carbon electrode surfaces for the detection and monitoring of hydrogen peroxide ( H2O2 ). The polymer-modified electrodes were characterized using electrochemical and microscopic-based methods. Atomic force microscopy (AFM) was used to study the bare and polymer-modified ITO surfaces. The electrocatalytic reduction of H2O2 with glassy carbon polymer-modified electrodes gave higher current densities compared to their gold counterparts. The electroanalytical properties of H2O2 were obtained using a real-time calibration curve of the amperometric determination in pH 7.4 aqueous solution. The limits of detection (LoD) of the polymer-modified electrodes towards electroreduction of H2O2 were of the order of 10–7 M, with high sensitivity ranging from 6.0–15.4 mA.mM-1.cm-2.

Probing electrochemical and electrocatalytic properties of cobalt(II) and manganese(III) octakis(hexylthio)phthalocyanine as self-assembled monolayers

New peripherally (β) and non-peripherally (α) substituted metal octakis(hexylthio)phthalocyanines (β- and α-MOcHexTPc) containing cobalt and manganese as metal centers were synthesized. Their characterization using electrochemical methods showed that these complexes exhibit several redox processes at E1/2 (mV vs. Ag∣AgCl) = 380 (212) (I), 1140 (864) (II), -450 (-460) (III) and -1170 (-1304) (IV) for β- (α-) CoOcHexTPc . These redox processes were assigned to CoIIIPc-2/CoIIPc-2 (I) , CoIIIPc-1/CoIIIPc-2 (II) , CoIIPc-2/CoIPc-2 (III) and CoIPc-2/CoIPc-3 (IV) using spectroelectrochemistry. For the β- (α-) MnOcHexTPc complex the redox processes were observed at E1/2 (mV vs. Ag∣AgCl) = -20 (5) (I), -530 (-640) (II) and -1270 (-1380) (III) and were assigned to MnIIIPc-2/MnIIPc-2 (I), MnIIPc-2/MnIIPc-3 (II) and MnIIPc-3/MnIIPc-4 (III) . Electrochemical and microscopic characterization using AFM showed that the self-assembled monolayers (SAMs) are formed on the gold surface using these complexes. The electrochemical characterization showed the blocking of the Faradaic processes at SAMs modified electrodes and these reactions are well-known to easily occur at unmodified gold electrodes. The AFM characterization showed an increase in surface roughness upon modifying the gold surface with MOcHexTPc SAMs, further confirming the presence of the monolayers on the gold surface. The MOcHexTPc SAMs were investigated for their electrocatalytic application towards H2O2 detection. The MOcHexTPc SAMs modified gold electrodes gave excellent currents for H2O2 detection. The observed H 2 O2 electrocatalytic reduction peaks were close to where the metal redox processes from the MOcHexTPc occurred, showing the involvement of the metal redox processes in the electrocatalytic mediation reactions.

Electrocatalytic and photosensitizing behavior of metallophthalocyanine complexes

Electrocatalytic or photosensitizing (photocatalytic) properties of metallophthalocyanine (MPc) complexes are dependent on the central metal. Electrocatalytic behavior is observed for electroactive central metals such as Co , Mn and Fe , whereas photosensitizing behavior is observed for diamagnetic metals such as Al , Zn and Si . In the presence of nanoparticles such as quantum dots, the photosensitizing behavior of MPc complexes is improved. Carbon nanotubes enhance the electrocatalytic behavior of MPc complexes.