Porphyrin-Based Nanostructures for Photocatalytic Applications

Probing mechanism of Rhodamine B decolorization under homogeneous conditions via pH-controlled photocatalysis with anionic porphyrin

Porphyrins are acknowledged for their efficacy as photosensitizers and show potential for the treatment of water contaminated with diverse dyes. This research emphasizes the use of meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) as a photosensitizer for purifying water contaminated with rhodamine B. Investigations were conducted under homogeneous conditions using visible light irradiation, revealing the efficacy of the porphyrin in the decolorization of rhodamine B strongly depends on pH of the solution. This study demonstrated that within 120 min, the decolorization process rapidly removed about 95% of RhB at an initial pH of 3.0, while at pH 6.0, the removal rate was significantly lower, at only 12%. An extensive photophysical study of the TPPS was carried out at pH 6.0 and pH 3.0 including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, triplet and singlet oxygen quantum yields in order to explain difference in the efficiency of RhB discoloration. A thorough investigation into mechanism revealed that neither reactive oxygen species nor singlet oxygen played a role in RhB decolorization within this system. Instead, the predominant route was found to be the electron transfer from photoexcited TPPS to RhB, followed by proton transfer at pH 3.0, leading to the generation of a colorless leuco form.

Supramolecular Self-Assembled Nanostructures Derived from Amplified Structural Isomerism of Zn(II)-Sn(IV)-Zn(II) Porphyrin Triads and Their Visible Light Photocatalytic Degradation of Pollutants

Two structural isomeric porphyrin-based triads (Zn(II)porphyrin-Sn(IV)porphyrin-Zn(II)porphyrin) denoted as T1 and T2 were prepared from the reaction of meso-[5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrinato]zinc(II) (ZnL) with trans-dihydroxo-[5,10-bis(3-pyridyl)-15,20-bis(phenyl)porphyrinato]tin(IV) (SnP1) and trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP2), respectively. All the compounds were characterized using UV-vis spectroscopy, emission spectroscopy, ESI-MS, 1H NMR spectroscopy, and FE-SEM. Most importantly, the two structurally isomeric porphyrin-based triads supramolecularly self-assembled into completely different nanostructures. T1 exhibits a nanosphere morphology, whereas T2 exhibits a nanofiber morphology. The amplified geometric feature in the structural isomeric porphyrin-based triads dictates the physical and chemical properties of the two triads. Both compounds showed the morphology-dependent visible light catalytic photodegradation of rhodamine B dye (74-97% within 90 min) and tetracycline antibiotic (44-71% within 45 min) in water. In both cases, the photodegradation efficiency of T2 was higher than that of T1. The present investigation can significantly contribute to the remediation of wastewater by tuning the conformational changes in porphyrin-based photocatalysts.

Sn(IV)porphyrin-Incorporated TiO2 Nanotubes for Visible Light-Active Photocatalysis

In this study, two distinct photocatalysts, namely tin(IV)porphyrin-sensitized titanium dioxide nanotubes (SnP-TNTs) and titanium dioxide nanofibers (TNFs), were synthesized and characterized using various spectroscopic techniques. SnP-TNTs were formed through the hydrothermal reaction of NaOH with TiO2 (P-25) nanospheres in the presence of Sn(IV)porphyrin (SnP), resulting in a transformation into Sn(IV)porphyrin-imbedded nanotubes. In contrast, under similar reaction conditions but in the absence of SnP, TiO2 (P-25) nanospheres evolved into nanofibers (TNFs). Comparative analysis revealed that SnP-TNTs exhibited a remarkable enhancement in the visible light photodegradation of model pollutants compared to SnP, TiO2 (P-25), or TNFs. The superior photodegradation activity of SnP-TNTs was primarily attributed to synergistic effects between TiO2 (P-25) and SnP, leading to altered conformational frameworks, increased surface area, enhanced thermo-chemical stability, unique morphology, and outstanding visible light photodegradation of cationic methylene blue dye (MB dye). With a rapid removal rate of 95% within 100 min (rate constant = 0.0277 min-1), SnP-TNTs demonstrated excellent dye degradation capacity, high reusability, and low catalyst loading, positioning them as more efficient than conventional catalysts. This report introduces a novel direction for porphyrin-incorporated catalytic systems, holding significance for future applications in environmental remediation.

Facile construction of multifunctional xNiCo2O4/BiVO4 heterojunction with accelerated charge transfer for efficient photocatalytic treatment of Cr (VI), MB and TC under visible light

The release of industrial effluents, comprising of organic dyes, antibiotics, and heavy metals poses substantial environmental and ecological threats. Among the different approaches, the utilization of heterogeneous photocatalysis based on semiconducting metal oxides is of paramount important to removal of organic ( MB dye and TC antibiotic) and inorganic pollutants ( Cr (VI) ) in wastewater. In this work, a new approach for creating type-II heterojunction photocatalysts named xNiCo2O4/BiVO4 or BNC is suggested. The as-prepared samples were thoroughly examined by means of several sophisticated analytical tools to investigate their physicochemical properties. These composites were utilized in the decomposition of MB dye, TC drug and the reduction of Cr (VI) under visible light irradiation. According to the findings, the creation of type-II heterojunction at BiVO4-NiCo2O4 interface greatly improved charge transportation while successfully preventing electron-hole recombination. Among the various composites studied, BNC-2 demonstrated an enhanced photocatalytic activity towards degradation of MB and TC, which were found to be 91 % over a period of 150 min and 95 % within only 60 min, respectively. Moreover, the photocatalytic reduction of Cr (VI) was accomplished 96 % within just 25 min. Additionally, it is discovered that BNC-2 displayed promising photostability and recyclability with a retention of >90 % after five consecutive cycles. The enhanced photocatalytic activity of BNC-2 is evidently attributed to the expedited separation and transfer of charges, as proven by photocurrent measurement, photoluminescence and electrochemical impedance spectroscopy analyses. Hence, the current amalgamation of NiCo2O4 and BiVO4 heterojunction composite has paved novel paths towards photocatalytic removal of organic as well as inorganic contaminants.

2D Metal-Organic Framework Nanosheets based on Pd-TCPP as Photocatalysts for Highly Improved Hydrogen Evolution

In this report, a 2D MOF nanosheet derived Pd single-atom catalyst, denoted as Pd-MOF, was fabricated and examined for visible light photocatalytic hydrogen evolution reaction (HER). This Pd-MOF can provide a remarkable photocatalytic activity (a H2 production rate of 21.3 mmol/gh in the visible range), which outperforms recently reported Pt-MOFs (with a H2 production rate of 6.6 mmol/gh) with a similar noble metal loading. Notably, this high efficiency of Pd-MOF is not due to different chemical environment of the metal center, nor by changes in the spectral light absorption. The higher performance of the Pd-MOF in comparison to the analogue Pt-MOF is attributed to the longer lifetime of the photogenerated electron-hole pairs and higher charge transfer efficiency.

Porphyrin-Based Nanomaterials for the Photocatalytic Remediation of Wastewater: Recent Advances and Perspectives

Self-organized, well-defined porphyrin-based nanostructures with controllable sizes and morphologies are in high demand for the photodegradation of hazardous contaminants under sunlight. From this perspective, this review summarizes the development progress in the fabrication of porphyrin-based nanostructures by changing their synthetic strategies and designs. Porphyrin-based nanostructures can be fabricated using several methods, including ionic self-assembly, metal-ligand coordination, reprecipitation, and surfactant-assisted methods. The synthetic utility of porphyrins permits the organization of porphyrin building blocks into nanostructures, which can remarkably improve their light-harvesting properties and photostability. The tunable functionalization and distinctive structures of porphyrin nanomaterials trigger the junction of the charge-transfer mechanism and facilitate the photodegradation of pollutant dyes. Finally, porphyrin nanomaterials or porphyrin/metal nanohybrids are explored to amplify their photocatalytic efficiency.

Enhancing Visible-Light Photocatalysis with Pd(II) Porphyrin-Based TiO2 Hybrid Nanomaterials: Preparation, Characterization, ROS Generation, and Photocatalytic Activity

Novel hybrid TiO2-based materials were obtained by adsorption of two different porphyrins on the surface of nanoparticles-commercially available 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and properly modified metalloporphyrin-5,10,15,20-tetrakis(2,6-difluoro-3-sulfophenyl)porphyrin palladium(II) (PdF2POH). The immobilization of porphyrins on the surface of TiO2 was possible due to the presence of sulfonyl groups. To further elevate the adsorption of porphyrin, an anchoring linker-4-hydroxybenzoic acid (PHBA)-was used. The synthesis of hybrid materials was proven by electronic absorption spectroscopy, dynamic light scattering (DLS), and photoelectrochemistry. Results prove the successful photosensitization of TiO2 to visible light by both porphyrins. However, the presence of the palladium ion in the modifier structure played a key role in strong adsorption, enhanced charge separation, and thus effective photosensitization. The incorporation of halogenated metalloporphyrins into TiO2 facilitates the enhancement of the comprehensive characteristics of the investigated materials and enables the evaluation of their performance under visible light. The effectiveness of reactive oxygen species (ROS) generation was also determined. Porphyrin-based materials with the addition of PHBA seemed to generate ROS more effectively than other composites. Interestingly, modifications influenced the generation of singlet oxygen for TPPS but not hydroxyl radical, in contrast to PdF2POH, where singlet oxygen generation was not influenced but hydroxyl radical generation was increased. Palladium (II) porphyrin-modified materials were characterized by higher photostability than TPPS-based nanostructures, as TPPS@PHBA-P25 materials showed the highest singlet oxygen generation and may be oxidized during light exposure. Photocatalytic activity tests with two model pollutants-methylene blue (MB) and the opioid drug tramadol (TRML)-confirmed the light dose-dependent degradation of those two compounds, especially PdF2POH@P25, which led to the virtually complete degradation of MB.

Self-assembled micro and nano rod-shaped porphyrin@Bi12O17Cl2 composite as an efficient photocatalyst for degradation of organic contaminants

Bi12O17Cl2 is a potential photocatalyst in practical applications due to its excellent photostability, visible light activity, and competitive bandgap energy. However, the fast recombination of photogenerated charge carriers makes it impractical for pollution mitigation. Recently, aggregated porphyrins have emerged as photosensitizers in light-dependent applications such as photocatalysis. Although Bi12O17Cl2 and porphyrin can function as separate photocatalysts, their photocatalytic properties in terms of visible light adsorption, charge separation and transport, can be improved when they are combined to form heterostructure. In this study, rod-shaped aggregated 5,10,15, 20-Tetrakis (4-carboxyphenyl) porphyrin was synthesized by CTAB-assisted, self-assembly strategy and Bi12O17Cl2 by a facile microwave method. The porphyrin and Bi12O17Cl2 were combined to generate a series of x%Porphyrin@Bi12O17Cl2 having 0.02% wt., 0.1% wt., 0.4% wt., 1% wt. and 10% wt. as compositions of porphyrin. The materials' photocatalytic degradation efficiency was tested on Rhodamine B dye as a representative pollutant. The best and worst performances were reported for 1%Porphyrin@Bi12O17Cl2 and 10%Porphyrin@Bi12O17Cl2, respectively, which are 3.1 and 0.5 times increases in efficiency compared to pure Bi12O17Cl2. From the radical trapping experiment, electrons and superoxide were the dominant reactive species in the degradation process. The enhanced photocatalytic capability of the materials was attributed to the photosensitizing property of porphyrin and the heterojunction formation, which promotes the separation of photogenerated charge carriers. A plausible step-scheme (S-scheme) was proposed for the photocatalytic degradation mechanism. The S-scheme provided the high redox potential of the photogenerated charge carriers. The findings herein offer a new option for improving the photocatalytic performance of Bi12O17Cl2 for environmental applications through the photosensitization strategy.

A Review of the Current State of Magnetic Force Microscopy to Unravel the Magnetic Properties of Nanomaterials Applied in Biological Systems and Future Directions for Quantum Technologies

Magnetism plays a pivotal role in many biological systems. However, the intensity of the magnetic forces exerted between magnetic bodies is usually low, which demands the development of ultra-sensitivity tools for proper sensing. In this framework, magnetic force microscopy (MFM) offers excellent lateral resolution and the possibility of conducting single-molecule studies like other single-probe microscopy (SPM) techniques. This comprehensive review attempts to describe the paramount importance of magnetic forces for biological applications by highlighting MFM's main advantages but also intrinsic limitations. While the working principles are described in depth, the article also focuses on novel micro- and nanofabrication procedures for MFM tips, which enhance the magnetic response signal of tested biomaterials compared to commercial nanoprobes. This work also depicts some relevant examples where MFM can quantitatively assess the magnetic performance of nanomaterials involved in biological systems, including magnetotactic bacteria, cryptochrome flavoproteins, and magnetic nanoparticles that can interact with animal tissues. Additionally, the most promising perspectives in this field are highlighted to make the reader aware of upcoming challenges when aiming toward quantum technologies.

Nanomaterials Aspects for Photocatalysis as Potential for the Inactivation of COVID-19 Virus

Coronavirus disease-2019 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is the most difficult recent global outbreak. Semiconducting materials can be used as effective photocatalysts in photoactive technology by generating various reactive oxidative species (ROS), including superoxide (•O2−) and hydroxyl (•OH) radicals, either by degradation of proteins, DNA, and RNA or by inhibition of cell development through terminating the cellular membrane. This review emphasizes the capability of photocatalysis as a reliable, economical, and fast-preferred method with high chemical and thermal stability for the deactivation and degradation of SARS-CoV-2. The light-generated holes present in the valence band (VB) have strong oxidizing properties, which result in the oxidation of surface proteins and their inactivation under light illumination. In addition, this review discusses the most recent photocatalytic systems, including metals, metal oxides, carbonaceous nanomaterials, and 2-dimensional advanced structures, for efficient SARS-CoV-2 inactivation using different photocatalytic experimental parameters. Finally, this review article summarizes the limitations of these photocatalytic approaches and provides recommendations for preserving the antiviral properties of photocatalysts, large-scale treatment, green sustainable treatment, and reducing the overall expenditure for applications.

Computational study of ground-state properties of μ2 -bridged group 14 porphyrinic sandwich complexes

The structural properties of μ₂ -bridged porphyrinic double-decker complexes are investigated and the influence of various ligands, metals, substituents, and bridging atoms on the dominant structural motif is elucidated. A variety of quantum chemical methods including semiempirical (SQM) methods and density functional theory (DFT) is assessed for the calculation of ecliptic and staggered conformational energies. Local coupled cluster (DLPNO-CCSD(T1)) data are generated for reference. The r² SCAN-3c composite scheme as well as the B2PLYP-D4/def2-QZVPP approach are identified as reliable methods. Energy decomposition analyses (EDA) and localized molecular orbital analyses (LMO) are used to investigate the bonding situation and the nature of the inter-ligand interaction energy underlining the crucial role of attractive London dispersion interactions. Targeted modification of the bridging atom, e.g., by replacing O^2- by S^2- is shown to drastically change the major structural features of the investigated complexes. Further, the influence of different substituents of varying size at the phthalocyanine ligand regarding the dominant conformation is described.

Temperature- and pH-Responsive Polymeric Photocatalysts for Enhanced Control and Recovery

The emergence of heterogeneous photocatalysis has facilitated redox reactions with high efficiency, without compromising the recyclability of the photocatalyst. Recently, stimuli-responsive heterogeneous photocatalytic materials have emerged as a powerful synthetic tool, with simple and rapid recovery, as well as an enhanced dynamic control over reactions. Stimuli-responsive polymers are often inexpensive and easy to produce. They can be switched from an active "on" state to an inert "off" state in response to external stimuli, allowing the production of photocatalyst with adaptability, recyclability, and orthogonal control on different chemical reactions. Despite this versatility, the application of artificial smart material in the field of heterogeneous photocatalysis has not yet been maximized. In this Minireview, we will examine the recent developments of this emerging class of stimuli-responsive heterogeneous photocatalytic systems. We will discuss the synthesis route of appending photoactive components into different triggerable systems and, in particular, the controlled activation and recovery of the materials.

Stereospecific Self-Assembly Processes of Porphyrin-Proline Conjugates: From the Effect of Structural Features and Bulk Solvent Properties to the Application in Stereoselective Sensor Systems

Conjugating the porphyrin ring with an amino acid via amide linkage represents a straightforward way for conferring both amphiphilicity and chirality to the macrocycle. Proline residue is a good choice in this context since its conformational rigidity allows for porphyrin assembling where molecular chirality is efficiently transferred and amplified using properly honed aqueous environments. Herein, we describe the evolution of the studies carried out by our group to achieve chiral systems from some porphyrin-proline derivatives, both in solution and in the solid state. The discussion focuses on some fundamental aspects reflecting on the final molecular architectures obtained, which are related to the nature of the appended group (stereochemistry and charge), the presence of a metal ion coordinated to the porphyrin core and the bulk solvent properties. Indeed, fine-tuning the mentioned parameters enables the achievement of stereospecific structures with distinctive chiroptical and morphological features. Solid films based on these chiral systems were also obtained and their recognition abilities in gaseous and liquid phase are here described.

Porphyrin-Nanocarbon Complexes to Control the Photodegradation of Rhodamine

Porphyrin-nanocarbon systems were used to generate a photocatalyst for the control of rhodamine B and rhodamine 6G photodegradation. Carboxylic functionalized multi-walled carbon nanotubes (o-MWCNTs) were decorated by two different porphyrin moieties: 5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (a-TPP) with an amine linker and 5-(4-carboxyphenyl)-10,15,20-(triphenyl)porphyrin (c-TPP) with a carboxyl linker to the o-MWCNT, respectively, with their photocatalyst performances investigated. The optical properties of the mixed nanocomposite materials were investigated to reveal the intrinsic energy levels and mechanisms of degradation. The charge-transfer states of the o-MWCNTs were directly correlated with the performance of the complexes as well as the affinity of the porphyrin moiety to the o-MWCNT anchor, thus extending our understanding of energy-transfer kinetics in porphyrin-CNT systems. Both a-TPP and c-TPP o-MWCNT complexes offered improved photocatalytic performance for both RhB and Rh6G compared to the reference o-MWCNTs and both porphyrins in isolated form. The photocatalytic performance improved with higher concentration of o-MWCNTs in the complexed sample, indicating the presence of greater numbers of -H/-OH groups necessary to more efficient photodegradation. The large presence of the -H/-OH group in the complexes was expected and was related to the functionalization of the o-MWCNTs needed for high porphyrin attachment. However, the photocatalytic efficiency was affected at higher o-MWCNT concentrations due to the decomposition of the porphyrins and changes to the size of the CNT agglomerates, thus reducing the surface area of the reactant. These findings demonstrate a system that displays solar-based degradation of rhodamine moieties that are on par, or an improvement to, state-of-the-art organic systems.

Sn(IV)-Porphyrin-Based Nanostructures Featuring Pd(II)-Mediated Supramolecular Arrays and Their Photocatalytic Degradation of Acid Orange 7 Dye

Two robust Sn(IV)-porphyrin-based supramolecular arrays (1 and 2) were synthesized via the reaction of trans-Pd(PhCN)2Cl2 with two precursor building blocks (SnP1 and SnP2). The structural patterns in these architectures vary from 2D to 3D depending on the axial ligation of Sn(IV)-porphyrin units. A discrete 2D tetrameric supramolecule (1) was constructed by coordination of {(trans-dihydroxo)[5,10-bis(4-pyridyl)-15,20-bis(phenyl) porphyrinato]}tin(IV) (SnP1) with trans-PdCl2 units. In contrast, the coordination between the {(trans-diisonicotinato)[5,10-bis(4-pyridyl)-15,20-bis(phenyl)porphyrinato]}tin(IV) (SnP2) and trans-PdCl2 units formed a divergent 3D array (2). Axial ligation of the Sn(IV)-porphyrin building blocks not only alters the supramolecular arrays but also significantly modifies the nanostructures, including porosity, surface area, stability, and morphology. These structural changes consequently affected the photocatalytic degradation efficiency under visible-light irradiation towards acid orange 7 (AO) dye in an aqueous solution. The degradation efficiency of the AO dye in the aqueous solution was observed to be between 86% to 91% within 90 min by these photocatalysts.

The pH Influence on the Water-Splitting Electrocatalytic Activity of Graphite Electrodes Modified with Symmetrically Substituted Metalloporphyrins

Hydrogen, considered to be an alternative fuel to traditional fossil fuels, can be generated by splitting water molecules into hydrogen and oxygen via the use of electrical energy, in a process whose efficiency depends directly on the employed catalytic material. The current study takes part in the relentless search for suitable and low-cost catalysts relevant to the water-splitting field by investigating the electrocatalytic properties of the O₂ and H₂ evolution reactions (OER and HER) of two metalloporphyrins: Zn(II) 5,10,15,20-tetrakis(4-pyridyl)-porphyrin and Co(II) 5,10,15,20-tetrakis(3-hydroxyphenyl)-porphyrin. The TEM/STEM characterisation of the porphyrin samples obtained using different organic solvents revealed several types of self-assembled aggregates. The HER and OER experiments performed on porphyrin-modified graphite electrodes in media with different pH values revealed the most electrocatalytically active specimens. For the OER, this specimen was the electrode manufactured with one layer of Co-porphyrin applied from dimethylsulfoxide, exhibiting an overpotential of 0.51 V at i = 10 mA/cm² and a Tafel slope of 0.27 V/dec. For the HER, it was the sample obtained by drop casting one layer of Zn-porphyrin from N,N-dimethylformamide that displayed a HER overpotential of 0.52 V at i = -10 mA/cm² and a Tafel slope of 0.15 V/dec.

Sn(IV) Porphyrin-Based Ionic Self-Assembled Nanostructures and Their Application in Visible Light Photo-Degradation of Malachite Green

A series of porphyrin-based ionic complexes were prepared through the reaction of two porphyrin precursors, 5,10,15,20-tetrakis(4-(2-pyridyl)phenyl)porphyrin H2TPhPyP (1) and trans-dihydroxo [5,10,15,20-tetrakis(4-(2-pyridyl)phenyl)porphyrinato]tin(IV) Sn(OH)2TPhPyP (2), with various acids (HCl, HNO3, CF3COOH, H2SO4, H2CO3, and H3PO4). The complexes were characterized via elemental analysis, 1H nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet (UV)-visible spectroscopy, fluorescence spectroscopy, and field-emission scanning electron microscopy (FE-SEM). Each compound exhibited different results for UV-visible, fluorescence, FT-IR, and FE-SEM studies depending on the counter anions. The complexes possessed different self-assembled nanostructures based on electronic interactions between the cations of compounds 1 and 2 with different counter anions. These aggregated species are stabilized by electrostatic forces and the π-π stacking interactions between the two porphyrin rings, in which the counter anions play an important bridging role. The counter anions also play an important role in controlling the morphology and photocatalytic properties of the as-developed materials. The complexes were then used for the photocatalytic degradation of the malachite green (MG) dye in aqueous media under visible light irradiation for up to 70 min. A morphology-dependent photocatalytic degradation of the MG dye was observed for all the ionic complexes, with efficiencies ranging from 50% to 95%.

Interplay between π-Conjugation and Exchange Magnetism in One-Dimensional Porphyrinoid Polymers

The synthesis of novel polymeric materials with porphyrinoid compounds as key components of the repeating units attracts widespread interest from several scientific fields in view of their extraordinary variety of functional properties with potential applications in a wide range of highly significant technologies. The vast majority of such polymers present a closed-shell ground state, and, only recently, as the result of improved synthetic strategies, the engineering of open-shell porphyrinoid polymers with spin delocalization along the conjugation length has been achieved. Here, we present a combined strategy toward the fabrication of one-dimensional porphyrinoid-based polymers homocoupled via surface-catalyzed [3 + 3] cycloaromatization of isopropyl substituents on Au(111). Scanning tunneling microscopy and noncontact atomic force microscopy describe the thermal-activated intra- and intermolecular oxidative ring closure reactions as well as the controlled tip-induced hydrogen dissociation from the porphyrinoid units. In addition, scanning tunneling spectroscopy measurements, complemented by computational investigations, reveal the open-shell character, that is, the antiferromagnetic singlet ground state (S = 0) of the formed polymers, characterized by singlet-triplet inelastic excitations observed between spins of adjacent porphyrinoid units. Our approach sheds light on the crucial relevance of the π-conjugation in the correlations between spins, while expanding the on-surface synthesis toolbox and opening avenues toward the synthesis of innovative functional nanomaterials with prospects in carbon-based spintronics.

Synthesis, Characterization, DFT and Photocatalytic Studies of a New Pyrazine Cadmium(II) Tetrakis(4-methoxy-phenyl)-porphyrin Compound

This study describes the synthesis, theoretical investigations, and photocatalytic degradational properties of a new (pyrazine)(meso-tetrakis(4-tert-methoxyphenyl)-porphyrinato)-cadmium (II) ([Cd(TMPP)-Pyz]) complex (1). The new penta-coordinated Cd^II porphyrin complex (1) was characterized by various spectroscopic techniques, including FT-IR, NMR, UV-visible absorption, fluorescence emission, and singlet oxygen, while its molecular structure was studied using single crystal X-ray diffraction. The UV–Vis spectroscopic study highlighted the redshift of the absorption bands after the insertion of the Cd(II) metal ion into the TMPP ring. The co-coordination of the pyrazine axial ligand enhanced this effect. A fluorescence emission spectroscopic study showed a significant blueshift in the Q bands, accompanied by a decrease in the fluorescence emission intensity and quantum yields of Φ_f = 0.084, Φ_f = 0.06 and Φ_f = 0.03 for H₂-TMPP free-base porphyrin, [Cd(TMPP)] and [Cd(TMPP)(Pyz)] (1) respectively. Singlet oxygen revealed that the H₂-TMPP porphyrin produced the most efficient singlet oxygen quantum yield of (Φ_Δ = 0.73) compared to [CdTMPP] (Φ_Δ = 0.57) and [Cd(TMPP)(Pyz)] (1) (Φ_Δ = 0.13). In the crystal lattice, the [Cd(TMPP)Pyz] was stabilized through non-covalent intermolecular interactions (NCI), such as the hydrogen bonds C-H···N and C-H···Cg. Additionally, crystal explorer software was then utilized to measure the quantitative analysis of the intermolecular interactions in the unit cell of the crystal structure and established that the C-H···π interaction dominated. The Natural bond orbital (NBO) analysis revealed that each molecule is stabilized by hyperconjugation and charge delocalization. As a photocatalyst, the coordination complex 1 showed excellent photocatalytic activity toward the degradation of Levafix Blue CA reactive dye (i.e., dye photo-degradation of 80%).

Regulation of the Assembled Structure of a Flexible Porphyrin Derivative Containing Tetra Isophthalic Acids by Coronene or Different Pyridines

Based on previous research, a new coassembly formed by a porphyrin derivative (IPETPP), which contains a flexible substituent of m-phthalic acid, is observed with coronene (COR) molecules at a higher concentration. Besides, a fresh IPETPP self-assembly formed at a lower concentration and another new coassembly with COR molecules are obtained. Moreover, the addition of a series of bipyridines alters the diamond arrangement of IPETPP, which enhances the stability of the two-component structures. It is unprecedented that bipyridine derivatives break intermolecular hydrogen bonds containing m-phthalic acid substituents. All the coassemblies are investigated by scanning tunneling microscopy on a highly oriented pyrolytic graphite. Combined with density functional theory, the formation mechanism of the assembled structures is revealed. These results would contribute to understanding the interfacial crystal behaviors and probably provide an efficient pathway to regulate the binary structures.

Self-Assembled Porphyrin Nanoleaves with Unique Crossed Transportation of Photogenerated Carriers to Enhance Photocatalytic Hydrogen Production

The preparation of self-assembled porphyrins with orderly stacked nanostructures for emulating natural photosynthesis has stimulated extensive efforts to optimize the energy conversion efficiency. However, the elucidation of how orderly stacked structures promote photocatalysis at the molecular level remains a great challenge. Here, unique porphyrin nanoleaves with designed and ordered structure are synthesized and show a hydrogen evolution rate higher than that of commercial powder. Photodeposition of cocatalysts and Kelvin probe force microscopy measurement suggest selective aggregation of photogenerated electrons and holes at different active sites. Combined with theoretical calculations, we find that the orderly packing changes molecular symmetry and induces a molecular dipole, which increases linearly along the π-π stacking direction and forms a strong built-in electric field. The built-in electric field drives photogenerated electrons and holes for the unique crossed transportation along different directions. These findings reveal how orderly stacked structures promote photocatalysis and provide a novel approach for highly efficient water splitting.

Morphology-controlled self-assembled nanostructures of complementary metalloporphyrin triads obtained through tuning their intermolecular coordination and their photocatalytic degradation of Orange II dye

Tuning the intermolecular metal–ligand coordination mode in a series of (Zn–Sn–Zn) porphyrin triads resulted in the formation of specific nanostructured photocatalysts for the visible light photodegradation of Orange II dye.

Bio-based porphyrins pyropheophorbide a and its Zn-complex as performing visible-light photosensitizers for free-radical photopolymerization

A chlorophyll a derivative, namely pyropheophorbide a (Pyro), and the corresponding zinc (II) complex (Zn-Pyro) were used for the first time as performing visible-light photosensitizers (PS) for free-radical photopolymerization (FRP)...

1D alignment of Co(II) metalated porphyrin-napthalimide based self-assembled nanowires for photocatalytic hydrogen evolution

The splitting of water into hydrogen and oxygen under visible light is an emerging phenomenon in green energy technology. Nevertheless, selecting an appropriate photocatalyst is rather significant to enhance hydrogen production on a large scale. In this context, organic photocatalysts have received considerable attention owing to their larger surface area, control in diffusion adsorption, nanostructures and electronic properties. Herein, we have developed five either free base or transition metalated porphyrin-napthalimide based donor-acceptor systems (PN1-PN5) and studied their morphology, electronic properties and catalytic behaviour. Detailed studies suggest that the Co(II) substituent D-A system (PN2) displayed a well-aligned one-dimensional (1D) nanowire with high electrical conductivity promoting remarkable photocatalytic hydrogen production rate (18 mM g^-1 h^-1) when compared to that of porphyrin-based derivatives reported until now. Thus, these results propose to investigate diverse metalated π-conjugated materials as photocatalysts for hydrogen production.

Application of a novel biomimetic double-ligand zirconium-based metal organic framework in environmental restoration and energy conversion

The development of visible-light response photocatalysts with a high catalytic performance and long-term cyclic stability is of great significance in the field of energy and environmental protection. Inspired by photosynthesis, a novel three-dimensional coral zirconium-based metal organic framework (MOF) was synthesized using a double-ligand strategy. The optimal sample, Zr-TCPP-bpydc (2:1), (the ratio of tetra-(4-carboxyphenyl) porphyrin to 2,2'-bipyridine-5,5'-dicarboxylic acid is 2:1) shows an excellent photocatalytic activity under visible light irradiation, and the effects of the amount of photocatalyst, pH and concentration on the degradation rate were investigated under the optimum conditions. It has a high degradation rate of tetracycline (98.12% for tetracycline and 96.74% for ofloxacin), which is 2.11 times higher than that of single ligand Zr-bpydc (zirconium-based MOF containing only 2,2'-bipyridine-5,5'-dicarboxylic acid). More importantly, it also has a good H₂ evolution rate (213.68 μmol g^-1h^-1) and CO₂ reduction (35.81 μmol g^-1h^-1). In addition, the intermediate pathway of degradation, photocatalytic enhancement mechanism and cycle stability were deeply studied by liquid chromatography-mass spectrometry (LC-MS), electron spin resonance spectroscopy (ESR), linear sweep voltammetry (LSV) and recycling tests. The synthesis of a three-dimensional biomimetic coral zirconium-based MOF material will provide guidance for the development of new, promising, and natural ideal photocatalytic materials.

Metallization-Prompted Robust Porphyrin-Based Hydrogen-Bonded Organic Frameworks for Photocatalytic CO2 Reduction

Under topological guidance, the self-assembly process based on a tetratopic porphyrin synthon results in a hydrogen-bonded organic framework (HOF) with the predicted square layers topology (sql) but unsatisfied stability. Strikingly, simply introducing a transition metal in the porphyrin center does not change the network topology but drastically causes noticeable change on noncovalent interaction, orbital overlap, and molecular geometry, therefore ultimately giving rise to a series of metalloporphyrinic HOFs with high surface area, and excellent stability (intact after being soaked in boiling water, concentrated HCl, and heated to 270 °C). On integrating both photosensitizers and catalytic sites into robust backbones, this series of HOFs can effectively catalyze the photoreduction of CO₂ to CO, and their catalytic performances greatly depend on the chelated metal species in the porphyrin centers. This work enriches the library of stable functional HOFs and expands their applications in photocatalytic CO₂ reduction.

High-performance porphyrin-like graphene quantum dots for immuno-sensing of Salmonella typhi

The extraordinary optical properties of porphyrins have inspired their applications in various fields. Herein, we introduce iron porphyrin bio-mimicked graphene quantum dots (Fe-N-GQDs) as a novel paramagnetic and fluorescent label. The Fe-N-GQD was prepared by the mechanochemical mixing of Fe, N, and C sources followed by pyrolysis at high-temperature and next, the solvothermal treatment was performed. The Fe-N sites in graphene matrix, the structural alterations during the solvothermal treatment, the optical properties, and paramagnetic behaviour were studied using FTIR, Raman and X-ray spectroscopies, and Vibrating sample magnetometer. The structural studies revealed that under solvothermal condition, Fe-N doped graphene sheets cut into ultra-small Fe-N-GQDs containing well-dispersed particles with an average diameter of about 2.5 nm. As a result of Fe-N doping, the photoluminescence quantum yield was enhanced to 86% and strong paramagnetic behaviour was observed. Due to the rich oxygen-containing groups at Fe-N-GQDs surface, it has proper sites for bio-conjugation. The bioconjugated Fe-N-GQDs serve as donors in a prominent fluorescence resonance energy transfer system, while graphene oxide acts as an acceptor. The proposed immunosensor was successfully applied for the detection of Salmonella Typhi Vi antigen in real human serum in the concentration range from 1 pg/mL to 1 μg/mL with the detection limit of 1 pg/mL.

Water-Soluble Non-Ionic PEGylated Porphyrins: A Versatile Category of Dyes for Basic Science and Applications

This review arises from the need to rationalize the huge amount of information on the structural and spectroscopic properties of a peculiar class of porphyrin derivatives-the non-ionic PEGylated porphyrins-collected during almost two decades of research. The lack of charged groups in the molecular architecture of these porphyrin derivatives is the leitmotif of the work and plays an outstanding role in highlighting those interactions between porphyrins, or between porphyrins and target molecules (e.g., hydrophobic-, hydrogen bond related-, and coordination-interactions, to name just a few) that are often masked by stronger electrostatic contributions. In addition, it is exactly these weaker interactions between porphyrins that make the aggregated forms more prone to couple efficiently with external perturbative fields like weak hydrodynamic vortexes or temperature gradients. In the absence of charge, solubility in water is very often achieved by covalent functionalization of the porphyrin ring with polyethylene glycol chains. Various modifications, including of chain length or the number of chains, the presence of a metal atom in the porphyrin core, or having two or more porphyrin rings in the molecular architecture, result in a wide range of properties. These encompass self-assembly with different aggregate morphology, molecular recognition of biomolecules, and different photophysical responses, which can be translated into numerous promising applications in the sensing and biomedical field, based on turn-on/turn-off fluorescence and on photogeneration of radical species.

Self-Assembled Nanomaterials Based on Complementary Sn(IV) and Zn(II)-Porphyrins, and Their Photocatalytic Degradation for Rhodamine B Dye

A series of porphyrin triads (1–6), based on the reaction of trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP) with six different phenoxy Zn(II)-porphyrins (ZnLⁿ), was synthesized. The cooperative metal–ligand coordination of 3-pyridyl nitrogens in the SnP with the phenoxy Zn(II)-porphyrins, followed by the self-assembly process, leads to the formation of nanostructures. The red-shifts and remarkable broadening of the absorption bands in the UV–vis spectra for the triads in CHCl₃ indicate that nanoaggregates may be produced in the self-assembly process of these triads. The emission intensities of the triads were also significantly reduced due to the aggregation. Microscopic analyses of the nanostructures of the triads reveal differences due to the different substituents on the axial Zn(II)-porphyrin moieties. All these nanomaterials exhibited efficient photocatalytic performances in the degradation of rhodamine B (RhB) dye under visible light irradiation, and the degradation efficiencies of RhB in aqueous solution were observed to be 72~95% within 4 h. In addition, the efficiency of the catalyst was not impaired, showing excellent recyclability even after being applied for the degradation of RhB in up to five cycles.

Spinel LiMn2O4 nanoparticles fabricated by the flexible soft template/Pichini method as cathode materials for aqueous lithium-ion capacitors with high energy and power density

Spinel LiMn2O4 (LMO) with a three-dimensional structure has become one of the cathode materials that has gained the most interest due to its safety, low price and abundant resources. However, the lithium ion transmission is limited by large particle size and particle agglomeration of LMO. Thus, reducing the particle size and agglomeration of LMO can effectively improve its lithium ion transmission. Here, we synthesized a LMO cathode material with a nanoscale crystal size using the flexible expanded graphite (EG) soft template and Pichini method. EG-controlled particle size and particle agglomeration of LMO is conducive to charge transfer and diffusion of lithium ions between LMO and the electrolyte, meanwhile, there are more redox sites on the nanosized LMO particles, which makes the redox reaction of LMO more thorough during the charge and discharge process, resulting in high capacitance performance. In order to obtain the considerably required lithium-ion capacitors (LICs) with high energy density and power density, we assembled aqueous LMO//activated carbon (AC) LICs with 5 M LiNO3 as the aqueous electrolytes, which are environmentally friendly, safe, low cost and have higher electrical conductivity than organic electrolytes. The optimal LIC has an energy density of 32.63 W h kg-1 at a power density of 500 W kg-1 and an energy density of 8.06 W h kg-1 at a power density of 10 000 W kg-1, which is higher than most of the LMO-based LICs in previous reports. After 2000 cycles, the specific capacitance retention rate was 75.9% at a current density of 3 A g-1. Therefore, our aqueous LMO//AC LICs synthesized by the soft template/Pichini method have wide prospects and are suitable for low-cost, high-safety and high-power applications.

Innovative Polymeric Hybrid Nanocomposites for Application in Photocatalysis

The immobilization of inorganic nanomaterials on polymeric substrates has been drawing a lot of attention in recent years owing to the extraordinary properties of the as-obtained materials. The hybrid materials, indeed, combine the benefits of the plastic matter such as flexibility, low-cost, mechanical stability and high durability, with them deriving from their inorganic counterparts. In particular, if the inorganic fillers are nanostructured photocatalysts, the originated hybrid systems will be able to utilize the energy delivered by light, catalysing chemical reactions in a sustainable pathway. Most importantly, since the nanofillers can be ad-hoc anchored to the macromolecular structure, their release in the environment will be prevented, thus overcoming one of the main restrictions that impedes their applications on a large scale. In this review, several typologies of hybrid photocatalytic nanomaterials, obtained by using both organic and inorganic semiconductors and realized with different synthetic protocols, were reported and discussed. In the first part of the manuscript, nanocomposites realized by simply blending the TiO2 or ZnO nanomaterials in thermoplastic polymeric matrices are illustrated. Subsequently, the atomic layer deposition (ALD) technique is presented as an excellent method to formulate polymeric nanocomposites. Successively, some examples of polyporphyrins hybrid systems containing graphene, acting as photocatalysts under visible light irradiation, are discussed. Lastly, photocatalytic polymeric nanosponges, with extraordinary adsorption properties, are shown. All the described materials were deeply characterized and their photocatalytic abilities were evaluated by the degradation of several organic water pollutants such as dyes, phenol, pesticides, drugs, and personal care products. The antibacterial performance was also evaluated for selected systems. The relevance of the obtained results is widely overviewed, opening the route for the application of such multifunctional photocatalytic hybrid materials in wastewater remediation.

Fluorescent nanorods based on 9,10-distyrylanthracene (DSA) derivatives for efficient and long-term bioimaging

Fluorescent nanoparticles based on 9,10-distyrylanthracene (DSA) derivatives (4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))bis(N,N-dimethylaniline) (NDSA) and 4,4'-((1E,1'E)-anthracene-9,10-diylbis(ethene-2,1-diyl))dibenzonitrile (CNDSA)) were prepared using an ultrasound aided nanoprecipitation method. The morphologies of the fluorescent nanoparticles could be controlled by adjusting the external ultrasonication time. NDSA or CNDSA could form spherical nanodots (NDSA NDs, CNDSA NDs) in a THF-H2O mixture with an 80% or 70% water fraction when the ultrasonication time was 30 s. When the ultrasonication time was prolonged to 10 min, NDSA and CNDSA could assemble into nanorods (NDSA NRs, CNDSA NRs). Meanwhile, the sizes of NDSA NRs and CNDSA NRs could be controlled by adjusting the water content in the mixture. As the water fraction was increased from 60% to 80%, the sizes of NDSA and CNDSA nanorods or nanodots reduced from 238.4 nm to 140.3 nm, and 482 nm to 198.4 nm, respectively. When the water fraction was up to 90%, irregular morphologies of NDSA and CNDSA could be observed. The nanoparticles exhibited intense fluorescence emission, good anti-photobleaching properties, as well as excellent stability and biocompatibility. In vitro cell imaging experiments indicated that the nanorods prepared by this simple method had the potential to be used for efficient and noninvasive long-term bioimaging.

Novel Cationic Meso-Arylporphyrins and Their Antiviral Activity against HSV-1

This work is devoted to the search for new antiherpes simplex virus type 1 (HSV-1) drugs among synthetic tetrapyrroles and to an investigation of their antiviral properties under nonphotodynamic conditions. In this study, novel amphiphilic 5,10,15,20-tetrakis(4-(3-pyridyl-n-propanoyl)oxyphenyl)porphyrin tetrabromide (3a), 5,10,15,20-tetrakis(4-(6-pyridyl-n-hexanoyl)oxyphenyl)porphyrin tetrabromide (3b) and known 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetraiodide (TMePyP) were synthesized, and their dark antiviral activity in vitro against HSV-1 was studied. The influence of porphyrin’s nanosized delivery vehicles based on Pluronic F127 on anti-HSV-1 activity was estimated. All the received compounds 3a, 3b and TMePyP showed virucidal efficiency and had an effect on viral replication stages. The new compound 3b showed the highest antiviral activity, close to 100%, with the lowest concentration, while the maximum TMePyP activity was observed with a high concentration; porphyrin 3a was the least active. The inclusion of the synthesized compounds in Pluronic F-127 polymeric micelles had a noticeable effect on antiviral activity only at higher porphyrin concentrations. Action of the received compounds differs by influence on the early or later reproduction stages. While 3a and TMePyP acted on all stages of the viral replication cycle, porphyrin 3b inhibited viral replication during the early stages of infection. The resulting compounds are promising for the development of utilitarian antiviral agents and, possibly, medical antiviral drugs.

Recent advances in electroanalytical drug detection by porphyrin/phthalocyanine macrocycles: developments and future perspectives

Porphyrins and phthalocyanines used to construct sensors for electroanalytical drug detection.

Zinc porphyrin/mesoporous titania thin film electrodes: a hybrid material nanoarchitecture for photocatalytic reduction

In this work, photocatalytic reduction of methyl viologen is achieved using zinc tetra(4-N-methylpyridyl)porphine (ZnP) functionalized mesoporous titania thin films (MTTF). Also, ZnP sensitizing and photophysical properties are retained in the hybrid material.

Supramolecular Porphyrin Nanostructures Based on Coordination-Driven Self-Assembly and Their Visible Light Catalytic Degradation of Methylene Blue Dye

A series of porphyrin triads (1–4), in which each triad is composed of a Sn(IV) porphyrin and two free-base (or Zn(II)) porphyrins, was synthesized and their self-assembled nanostructures were studied. Depending on the substituent on porphyrin moieties, each triad was self-assembled into a different nanostructure. In particular, the cooperative coordination of 3-pyridyl groups in the Sn(IV) porphyrin with the axial Zn(II) porphyrins in triad 4 leads to forming uniform nanofibers with an average width of 10–22 nm. Other triads without the coordinating interaction between the central Sn(IV) porphyrin and the axial porphyrins formed irregularly shaped aggregates in contrast. The morphologies of nanofiber changed drastically upon the addition of pyrrolidine, in which pyrrolidine molecules break down the self-assembly process by coordinating with the axial Zn(II) porphyrins. All porphyrin aggregates exhibited efficient photocatalytic performances on the degradation of methylene blue dye under visible light irradiation. The degradation efficiencies after 2 h were observed to be between 70% and 95% for the aggregates derived from the four triads.

DNA-damage and cell cycle arrest initiated anti-cancer potency of super tiny carbon dots on MCF7 cell line

While carbon-based materials have spearheaded numerous breakthroughs in biomedicine, they also have procreated many logical concerns on their overall toxicity. Carbon dots (CDs) as a respectively new member have been extensively explored in nucleus directed delivery and bioimaging due to their intrinsic fluorescence properties coupled with their small size and surface properties. Although various in vitro/in vivo studies have shown that CDs are mostly biocompatible, sufficient information is lacking regarding genotoxicity of them and underlying mechanisms. This study aims to analyze the real-time cytotoxicity of super tiny CDs (2.05 ± 0.22 nm) on human breast cancer cells (MCF7) and human primary dermal fibroblast cell cultures (HDFa) by xCELLigence analysis system for further evaluating their genotoxicity and clastogenicity to evaluate the anti-tumor potential of CDs on breast adenocarcinoma. As combined with flow cytometry studies, comet assay and cytokinesis-block micronucleus assay suggest that the CDs can penetrate to the cell nuclei, interact with the genetic material, and explode DNA damage and G0/G1 phase arrest in cancer cells even at very low concentrations (0.025 ppm) which provide a strong foundation for the design of potentially promising CD-based functional nanomaterials for DNA-damage induced treatment in cancer therapy.

Enhanced Photocatalytic CO2 Reduction over TiO2 Using Metalloporphyrin as the Cocatalyst

The photocatalytic reduction of carbon dioxide (CO2) into CO and hydrocarbon fuels has been considered as an ideal green technology for solar-to-chemical energy conversion. The separation/transport of photoinduced charge carriers and adsorption/activation of CO2 molecules play crucial roles in photocatalytic activity. Herein, tetrakis (4-carboxyphenyl) porphyrin (H2TCPP) was incorporated with different metal atoms in the center of a conjugate macrocycle, forming the metalloporphyrins TCPP-M (M = Co, Ni, Cu). The as-obtained metalloporphyrin was loaded as a cocatalyst on commercial titania (P25) to form TCPP-M@P25 (M = Co, Ni, Cu) for enhanced CO2 photoreduction. Among all of the TCPP-M@P25 (M = Co, Ni, Cu), TCPP-Cu@P25 exhibited the highest evolution rates of CO (13.6 μmol⋅g−1⋅h−1) and CH4 (1.0 μmol⋅g−1⋅h−1), which were 35.8 times and 97.0 times those of bare P25, respectively. The enhanced photocatalytic activity could be attributed to the improved photogenerated electron-hole separation efficiency, as well as the increased adsorption/activation sites provided by the metal centers in TCPP-M (M = Co, Ni, Cu). Our study indicates that metalloporphyrin could be used as a high-efficiency cocatalyst to enhance CO2 photoreduction activity.