Nickel (II) tetraphenylporphyrin modified surfaces via electrografting of an aryldiazonium salt

Fabrication of Mn-TPP/RGO Tailored Glassy Carbon Electrode for Doxorubicin Sensing

Cancer is a long-standing disease, and the use of anticancer drugs can cause many different harmful side effects. Therefore, the quantitative analysis of anticancer drugs is crucial. Among all the analytical techniques that have been utilized for the detection of doxorubicin, electrochemical sensors have drawn exceptional consideration because they are simple, affordable, and highly sensitive. Manganese tetraphenylporphyrin decorated reduced graphene oxide (Mn-TPP/RGO), tetraphenylporphyrin decorated reduced graphene oxide (TPP/RGO), and reduced graphene oxide (RGO) nanostructure based glassy carbon electrodes (GCEs) were fabricated for the detection of doxorubicin (DOX). The synthesized materials were characterized by FTIR, scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV/vis), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Doxorubicin detection was performed using differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Among the prepared electrodes, Mn-TPP/RGO modified GCE gave an optimum peak current at pH 3. The Mn-TPP/RGO modified electrode showed significant linear response range (0.1-0.6 mM); effective sensitivity (112.09 μA mM-1 cm-2); low detection limit (63.5 μM); and excellent stability, selectivity, repeatability, and reproducibility toward doxorubicin. With differential pulse voltammetry, LoD and sensitivity were 27 μM and 0.174 μA μM-1 cm-2, respectively. Real sample analysis was also performed in human serum, and it depicted reasonable recovery results for spiked doxorubicin.

Nitration of Porphyrin Systems: A Toolbox of Synthetic Methods

This review addresses nitration reactions of porphyrin derivatives. Simple porphyrins modifications afford valuable intermediates in this area of chemistry. They are useful materials for further transformations, as the NO₂ group introduced into parent porphyrin system increases its electrophilic character, thus allowing a broad spectrum of subsequent reactions, e. g. reduction of NO₂ to NH₂ , subsequent diazotisation, nucleophilic substitution of hydrogen (in ortho-position to NO₂ ), a variety of cyclizations, etc. Such reactions are often utilized in the first steps of the designed syntheses, leading to attractive and useful target porphyrin molecules. This approach (via nitro-derivatives) allows synthesizing numerous porphyrin-like compounds of a high degree of complexity, and has thus become one of the methods choice. The substitution by NO₂ group can take place at all positions of the porphyrin systems: four meso-positions (5, 10, 15, 20) and eight positions β (2, 3, 7, 8, 12, 13, 17, 18). The third possibility includes the nitration in meso-aryl rings attached to positions 5, 10, 15, and 20. The latter derivatives (meso-aryl substituted ones) are a large, well-known group of synthetic porphyrins. The nitration reactions described herein follow three various mechanisms: (a) radical, (b) via π-cation radicals and π-dications, and (c) electrophilic. All the above cases are discussed in detail. According to our knowledge, this is the first such systematic account concerning these reactions.

Ethynylphenyl-Derivatized Free Base Porphyrins: Anodic Oxidation Processes and Covalent Grafting onto Glassy Carbon Electrodes

In six of seven cases, direct anodic oxidation of the ethynyl group of an ethynylphenyl-derivatized free-base porphyrin gave modified glassy carbon electrodes in which the porphyrin was strongly surface-bound, most likely in a perpendicular geometry through covalent attachment of the ethynyl group to a surface carbon atom. The porphyrins each contained an ethynylphenyl group in one meso position and varied in the groups present in the other three meso positions. Electrografted 5,10,15,20-tetrakis(ethynylphenyl)porphyrin, H₂1, which has ethynyl moieties in all four meso positions, has well-defined surface voltammetry and grows to multilayer levels upon repeated cyclic voltammetry (CV) deposition scans. Multilayering was not observed to the same degree for monoethynylphenyl-substituted porphyrins and became progressively less for porphyrins having groups in the 15-meso position that were more protective against ethynyl radical attack. Clean molecular monolayer-level coverage was observed for 5-ethynylphenyl-10,20-bis(3-methoxyphenyl)-15-hexylporphyrin, H₂5. Owing to the fact that the ethynyl oxidation potential (1.1 to 1.5 V vs ferrocene) is more positive than that of the second macrocycle oxidation, the longevities and follow-up reactions of the porphyrin dications were also studied by CV, chemical oxidation, and optical spectroscopy in homogeneous solution. The primary follow-up products of the doubly oxidized porphyrins, whether surface-bound or in solution, were pyrrole-protonated species that were easily reduced back to the neutral porphyrin.

Use of calixarenes bearing diazonium groups for the development of robust monolayers with unique tailored properties

Calixarene-based diazonium salts can be easily synthesized in a few steps. This review surveys recent examples that illustrate the key advantages of these highly reactive molecular platforms for surface modification.

Diels-Alder Reaction of Anthranilic Acids: A Versatile Route to Dense Monolayers on Flat Edge and Basal Plane Graphitic Carbon Substrates

Methods that reliably yield monolayers of covalently anchored modifiers on graphene and other planar graphitic materials are in demand. Covalently bonded groups can add functionality to graphitic carbon for applications ranging from sensing to supercapacitors and can tune the electronic and optical properties of graphene. Limiting modification to a monolayer gives a layer with well-defined concentration and thickness providing a minimum barrier to charge transfer. Here we investigate the use of anthranilic acid derivatives for grafting aryl groups to few layer graphene and pyrolyzed photoresist film (PPF). Under mild conditions, anthranilic acids generate arynes, which undergo Diels-Alder cycloadditions. Using spectroscopy, electrochemistry, and atomic force microscopy, we demonstrate that the reaction yields monolayers of aryl groups on graphene and PPF with maximum surface coverages consistent with densely packed layers. Our study confirms that anthranilic acids offer a convenient route to covalent modification of planar graphitic carbons (both basal and edge plane materials).

Reduced graphene oxide/gold tetraphenyl porphyrin (RGO/Au–TPP) nanocomposite as an ultrasensitive amperometric sensor for environmentally toxic hydrazine

A gold tetra phenyl porphyrin/reduced graphene oxide (RGO/Au–TPP) nanocomposite film modified glassy carbon electrode (GCE) was prepared for the trace level detection of hydrazine.

Evidence of monolayer formation via diazonium grafting with a radical scavenger: electrochemical, AFM and XPS monitoring

AFM monitoring of controlled surface modification with a radical scavenger.

X-RAY PHOTOELECTRON SPECTROSCOPY AND SCANNING ELECTROCHEMICAL MICROSCOPY STUDIES OF BRANCHED MULTIWALLED CARBON NANOTUBE PAPER MODIFIED BY ELECTROCHEMICAL GRAFTING AND CLICK CHEMISTRY

Modification of nanomaterials through electrochemical grafting is a useful approach to introduce linking groups on to the surface of these structures. This work shows the possibility of applying electrochemical grafting to branched multiwalled carbon nanotube paper with an electrical resistance of 0.1 ohm-cm, and subsequent reaction of the grafted 4-azidobenzenediazonium with ethynylferrocene through the Sharpless click chemistry reaction. A comparison is made between this paper electrode and adsorbed single-walled carbon nanotubes on a glassy carbon electrode, with electrochemistry, X-ray photoelectron spectroscopy and scanning electrochemical microscopy used for characterization.