Self-Assembled One-Dimensional Porphyrin Nanostructures with Enhanced Photocatalytic Hydrogen Generation

Porphyrin Aggregation under Homogeneous Conditions Inhibits Electrocatalysis: A Case Study on CO2 Reduction

Metalloporphyrins are widely used as homogeneous electrocatalysts for transformations relevant to clean energy and sustainable organic synthesis. Metalloporphyrins are well-known to aggregate due to π-π stacking, but surprisingly, the influence of aggregation on homogeneous electrocatalytic performance has not been investigated previously. Herein, we present three structurally related iron meso-phenylporphyrins whose aggregation properties are different in commonly used N,N-dimethylformamide (DMF) electrolyte. Both spectroscopy and light scattering provide evidence of extensive porphyrin aggregation under conventional electrocatalytic conditions. Using the electrocatalytic reduction of CO2 to CO as a test reaction, cyclic voltammetry reveals an inverse dependence of the kinetics on the catalyst concentration. The inhibition extends to bulk performance, where up to 75% of the catalyst at 1 mM is inactive compared to at 0.25 mM. We additionally report how aggregation is perturbed by organic additives, axial ligands, and redox state. Periodic boundary calculations provide additional insights into aggregate stability as a function of metalloporphyrin structure. Finally, we generalize the aggregation phenomenon by surveying metalloporphyrins with different metals and substituents. This study demonstrates that homogeneous metalloporphyrins can aggregate severely in well-solubilizing organic electrolytes, that aggregation can be easily modulated through experimental conditions, and that the extent of aggregation must be considered for accurate catalytic benchmarking.

Hot carrier dynamics in metalated porphyrin-naphthalimide thin films

This study employs femtosecond transient absorption spectroscopy to investigate the rapid dynamics of excited state carriers in three metalated porphyrin-naphthalimide (PN) molecules and one free-base molecule. The dynamics of electron injection, from PN to mesoporous titania (TiO2), in PN adsorbed TiO2 films (Ti-PN), were carefully investigated and compared to PN adsorbed ZrO2 films (Zr-PN). In addition, we examined the self-assembled PN films and found that, in their self-assembled state, these molecules exhibited a longer relaxation time than Zr-PN monomeric films, where the charge injection channel was insignificant. The ground-state bleach band in the Ti-PN films gradually shifted to longer wavelengths, indicating the occurrence of the Stark effect. Faster electron injection was observed for the metalated PN systems and the electron injection times from the various excited states to the conduction band of TiO2 (CB-TiO2) were obtained from the target model analysis of the transient absorption spectra data matrix. In these metal-organic complexes, hot electron injection from PN to CB-TiO2 occurred on a time scale of <360 fs. Importantly, Cu(II)-based PN complexes exhibited faster injection and longer recombination times. The injection times have been estimated to result from a locally excited state at ≈280 fs, a hot singlet excited state at 4.95 ps, and a vibrationally relaxed singlet excited state at 97.88 ps. The critical photophysical and charge injection processes seen here provide the potential for exploring the underlying factors involved and how they correlate with photocatalytic performance.

Porphyrin-Based Self-Assembled Nanoparticles for PET/MR Imaging of Sentinel Lymph Node Metastasis

Diagnosing of lymph node metastasis is challenging sometimes, and multimodal imaging offers a promising method to improve the accuracy. This work developed porphyrin-based nanoparticles (68Ga-F127-TAPP/TCPP(Mn) NPs) as PET/MR dual-modal probes for lymph node metastasis imaging by a simple self-assembly method. Compared with F127-TCPP(Mn) NPs, F127-TAPP/TCPP(Mn) NPs synthesized by amino-porphyrins (TAPP) doping can not only construct PET/MR bimodal probes but also improve the T1 relaxivity (up to 456%). Moreover, T1 relaxivity can be adjusted by altering the molar ratio of TAPP/TCPP(Mn) and the concentration of F127. However, a similar increase in T1 relaxivity was not observed in the F127-TCPP/TCPP(Mn) NPs, which were synthesized using carboxy-porphyrins (TCPP) doping. In a breast cancer lymph node metastasis mice model, subcutaneous injection of 68Ga-F127-TAPP/TCPP(Mn) NPs through the hind foot pad, the normal lymph nodes and metastatic lymph nodes were successfully distinguished based on the difference of PET standard uptake values and MR signal intensities. Furthermore, the dark brown F127-TAPP/TCPP(Mn) NPs demonstrated the potential for staining and mapping lymph nodes. This study provides valuable insights into developing and applying PET/MR probes for lymph node metastasis imaging.

Self-assembled π-conjugated chromophores: preparation of one- and two-dimensional nanostructures and their use in photocatalysis

Photocatalytic systems have attracted research interest as a clean approach to generate energy from abundant sunlight. In this context, developing efficient and robust photocatalytic structures is crucial. Recently, self-assembled organic chromophores have entered the stage as alternatives to both molecular systems and (in)organic semiconductors. Nanostructures made of self-assembled π-conjugated dyes offer, on the one hand, molecular customizability to tune their optoelectronic properties and activities and on the other hand, provide benefits from heterogeneous catalysis that include ease of separation, recyclability and improved photophysical properties. In this contribution, we present recent achievements in constructing supramolecular photocatalytic systems made of chromophores for applications in water splitting, H2O2 evolution, CO2 reduction, or environmental remediation. We discuss strategies that can be used to prepare ordered photocatalytic systems with an emphasis on the effect of packing between the dyes and the resulting photocatalytic activity. We further showcase supramolecular strategies that allow interfacing the organic nanostructures with co-catalysts, molecules, polymers, and (in)organic materials. The principles discussed here are the foundation for the utilization of these self-assembled materials in photocatalysis.

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.

Near-Infrared-II-Activatable Self-Assembled Manganese Porphyrin-Gold Heterostructures for Photoacoustic Imaging-Guided Sonodynamic-Augmented Photothermal/Photodynamic Therapy

Porphyrins and their derivatives are widely used as photosensitizers and sonosensitizers in tumor treatment. Nevertheless, their poor water solubility and low chemical stability reduce their singlet oxygen (1O2) yield and, consequently, their photodynamic therapy (PDT) and sonodynamic therapy (SDT) efficiency. Although strategies for porphyrin molecule assembly have been developed to augment 1O2 generation, there is scope for further improving PDT and SDT efficiencies. Herein, we synthesized ordered manganese porphyrin (SM) nanoparticles with well-defined self-assembled metalloporphyrin networks that enabled efficient energy transfer for enhanced photocatalytic and sonocatalytic activity in 1O2 production. Subsequently, Au nanoparticles were grown in situ on the SM surface by anchoring the terminal alkynyl of porphyrin to form plasmonic SMA heterostructures, which showed the excellent near-infrared-II (NIR-II) region absorption and photothermal properties, and facilitated electron-hole pair separation and transfer. With the modification of hyaluronic acid (HA), SMAH heterostructure nanocomposites exhibited good water solubility and were actively targeted to cancer cells. Under NIR-II light and ultrasound (US) irradiation, the SMAH generates hyperthermia, and a large amount of 1O2, inducing cancer cell damage. Both in vitro and in vivo studies confirmed that the SMAH nanocomposites effectively suppressed tumor growth by decreasing GSH levels in SDT-augmented PDT/PTT. Moreover, by utilizing the strong absorption in the NIR-II window, SMAH nanocomposites can achieve NIR-II photoacoustic imaging-guided combined cancer treatment. This work provides a paradigm for enhancing the 1O2 yield of metalloporphyrins to improve the synergistic therapeutic effect of SDT/PDT/PTT.

Internal electric fields drive dual S-scheme heterojunctions: Insights into the role of the triple interlaced lattice

The internal electric field induced by the lattice interfaces in a heterojunction can facilitate charge transfer, thereby improving the photocatalytic performance. However, the details of the relationship between the lattice interfaces and the charge transfer mechanism in heterojunctions remain unclear. In this study, a Bi2WO6/Bi2O2CO3/C3N4 heterojunction (BBC) with an interlaced lattice was prepared, and the role of the interlaced lattice in charge transfer was revealed. Compared to pristine Bi2O2CO3, Bi2WO6, and C3N4, BBC exhibited an increased ciprofloxacin degradation rate constant (0.0573 min-1). A series of experiments were performed to reveal the role of the interlaced lattice interface in the enhanced photocatalytic performance. The results show that the driving force provided by the interlaced lattice interface changes the charge transfer mechanism from a dual Ⅱ-scheme to a dual S-scheme. This work provides profound insights into the effects of lattice interfaces in heterojunctions and the design of efficient photocatalysts.

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.

Making the connections: physical and electric interactions in biohybrid photosynthetic systems

Biohybrid photosynthesis systems, which combine biological and non-biological materials, have attracted recent interest in solar-to-chemical energy conversion. However, the solar efficiencies of such systems remain low, despite advances in both artificial photosynthesis and synthetic biology. Here we discuss the potential of conjugated organic materials as photosensitisers for biological hybrid systems compared to traditional inorganic semiconductors. Organic materials offer the ability to tune both photophysical properties and the specific physicochemical interactions between the photosensitiser and biological cells, thus improving stability and charge transfer. We highlight the state-of-the-art and opportunities for new approaches in designing new biohybrid systems. This perspective also summarises the current understanding of the underlying electron transport process and highlights the research areas that need to be pursued to underpin the development of hybrid photosynthesis systems.

Conducting 1D nanostructures from light-stimulated copper-metalated porphyrin-dibenzothiophene

Control over the dimensionality of stimulated organic semiconductors has aroused significant interest in organic electronics; however, the design of such materials still remains to be decided. Herein, we have developed three dibenzothiophene-appended freebase, zinc-metalated and copper-metalated porphyrin derivatives (PFb-DBT, PZn-DBT and PCu-DBT) in which PCu-DBT leads to an anion-binding complex in chloroform upon the application of light, resulting in self-assembled 1D nanostructures with high electrical conductivity. Nevertheless, light-stimulated freebase and zinc-metalated P-DBT undergo protonation and demetalation. Electron microscopic images displayed the anion-binding-assisted 1D nanostructure using weak non-covalent interactions, which promotes enhancement in electrical conductivity among other things, as confirmed by electrochemical impedance spectra. Thus, the generation of well-defined nanostructures with improved electronic characteristics from stimuli-responsive organic dyes suggests the importance of developing various smart materials for efficient field effect transistors and sensors.

Supermolecular Nanoentities of Vitamin B12 Derivative as a Link in the Evolution of the Parent Molecules During Self-Assembly at the Air-Water Interface

Nanoarchitectures with promising properties have now been formed from many important biomolecules. However, the preparation of nanoparticles of vitamin B₁₂ and its derivatives remains an ongoing research challenge. This paper describes the formation of supermolecular nanoentities (SMEs) of vitamin B₁₂ derivatives, unique nanoparticles with strong noncovalent intermolecular interactions, emerging properties, and activity. These were created by a nanoarchitectonic approach using directed assembly of layers at the air-water interface as a link in the chain of evolution of the parent molecules under specially created conditions. Such layers can be represented as a nanocosm, where, at a critical density, the assemblies act as nanoreactors in which the transformation of the original material occurs. The discovered SMEs not only replicate the functioning of vitamin B₁₂ assemblies with proteins in living organisms and act as vitamin B₁₂-depended enzymes but also demonstrate important advantages over vitamin B₁₂. They are more efficient in oxygen reduction/evolution reactions and in transformation into other forms. These SMEs, in performing advanced tasks, are an alternative to widely used materials based on noble metals for catalysis, medicine, and environment protection. Our findings open new perspectives both for the fabrication of novel SMEs of biomolecules and for a better understanding of the evolution of biomolecules in nature.

Hierarchically Organized Cocrystal of Tetra-Anionic Porphyrin and Di-Cationic Viologen: Ion Conformations, Supramolecule Interactions, and Porphyrin Arrays

Ionic co-assembly of tetra-anionic porphyrins has been extensively researched in the construction of hierarchically organized architectures with potential application value in organic semiconductors, sunlight catalysts and supramolecular chirality systems. However, such architectures are difficult to grow to a size suitable for single-crystal X-ray diffraction (SCXRD); the lack of single-crystal structures of these architectures leads to challenges in gaining deeper comprehension about that. This study reports a hierarchically organized cocrystal of meso-tetra(4-sulfonato-phenyl)-porphyrin (TSPP^4- ) and N, N'-diethyl-viologen (DEV²⁺ ), wherein wave-like and saddle-like TSPP^4- ions co-aggregate at a stoichiometric ratio of 1 : 2 to form unique porphyrin arrays; the spectrum characteristics and calculated coulombic exciton coupling energy show that these porphyrin arrays are J-aggregates. We prove that the distortion of porphyrin ring of TSPP^4- strongly correlates with the deflection of its phenyl groups. The crystal comprises six different ionic conformations, and the multiplicity of ionic conformation leads to intricate supramolecular interactions.

Noble Metal Nanoparticle-Loaded Porphyrin Hexagonal Submicrowires Composites (M-HW): Photocatalytic Synthesis and Enhanced Photocatalytic Activity

Surface plasmon resonance (SPR) photocatalysts have attracted considerable attention because of their strong absorption capacity of visible light and enhanced photogenic carrier separation efficiency. However, the separate production of metal nanoparticles (NPs) and semiconductors limits the photogenic charge transfer. As one of the most promising organic photocatalysts, porphyrin self-assemblies with a long-range ordered structure-enhance electron transfer. In this study, plasmonic noble metal-based porphyrin hexagonal submicrowires composites (M-HW) loaded with platinum (Pt), silver (Ag), gold (Au), and palladium (Pd) NPs were synthesized through a simple in situ photocatalytic method. Homogeneous and uniformly distributed metal particles on the M-HW composites enhanced the catalytic or chemical properties of the organic functional nanostructures. Under the same loading of metal NPs, the methyl orange photocatalytic degradation efficiency of Ag-HW [k_Ag-HW (0.043 min^-1)] composite was three times higher than that of HW, followed by Pt-HW [k_Pt-HW (0.0417 min^-1)], Au-HW [k_Au-HW (0.0312 min^-1)], and Pd-HW [k_Pd-HW (0.0198 min^-1)]. However, the rhodamine B (RhB) and eosin B photocatalytic degradations of Pt-HW were 4 times and 2.6 times those of HW, respectively. Finally, the SPR-induced electron injection, trapping, and recombination processes of the M-HW system were investigated. These results showed that M-HW plasmonic photocatalysts exhibited excellent photocatalytic performances, making them promising materials for photodegrading organic pollutants.

P-Induced In Situ Construction of ZnCoMOF@CoP-5 S-Scheme Heterojunctions for Enhanced Photocatalytic H2 Evolution

In view of the fact that the exposed catalytic active sites of single-metal MOFs cannot satisfy the efficient progress of the catalytic reaction, here we constructed a star-shaped bimetallic ZnCoMOF by introducing a Zn source by the partial ion exchange method and coprecipitation method. By controlling the quality of sodium hypophosphite, ZnCoMOF was subjected to different degrees of phosphating to optimize the experimental conditions. The introduction of the more electronegative P can attract more H⁺ to participate in the reduction reaction. The ZnCoMOF@CoP-5 S-scheme heterojunction was constructed in situ by generating CoP on the surface of ZnCoMOF under a PH₃ reducing atmosphere, which exhibited excellent H₂ evolution performance. This unique heterojunction effectively promotes the separation and transfer of e^--h⁺ pairs, ensuring a strong redox capability. The best hydrogen-evolution performance of ZnCoMOF@CoP-5 under the EY sensitization system reaches 16 958 μmol h^-1 g^-1, which has significant advantages over the same type of materials and similar photocatalytic hydrogen-evolution work. Finally, the photocatalytic mechanism was demonstrated by an in situ XPS technique. Our work provides important ideas for the research of bimetallic MOFs in the field of photocatalytic hydrogen evolution.

Porphyrins and phthalocyanines as biomimetic tools for photocatalytic H2 production and CO2 reduction

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H₂ is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO₂ into chemical fuels can reduce the CO₂ emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H₂ production and CO₂ reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application.

Surfactant-Free Green Synthesis of Au@Chlorophyll Nanorods for NIR PDT-Elicited CDT in Bladder Cancer Therapy

The facile and straightforward fabrication of NIR-responsive theranostic materials with high biocompatibility is still an unmet need for nanomedicine applications. Here, we used a natural photosensitizer, iron chlorophyll (Chl/Fe), for the J-aggregate template-assisted synthesis of Au@Chl/Fe nanorods with high stability. The assembly of a high amount of Chl/Fe J-aggregate onto the Au surface enabled red-NIR fluorescence for monitoring and tracking residential tumor lesions. The Chl/Fe moieties condensed on the nanorods could change the redox balance by the photon induction of reactive oxygen species and attenuate iron-mediated lipid peroxidation by inducing a Fenton-like reaction. After conjugation with carboxyphenylboronic acid (CPBA) to target the glycoprotein receptor on T24 bladder cancer (BC) cells, the enhanced delivery of Au@Chl/Fe-CPBA nanorods could induce over 85% cell death at extremely low concentrations of 0.16 ppm_[Au] at 660 nm and 1.6 ppm_[Au] at 785 nm. High lipid peroxidation, as shown by BODIPY staining and GSH depletion, was observed when treated T24 cells were exposed to laser irradiation, suggesting that preliminary photodynamic therapy (PDT) can revitalize Fenton-like reaction-mediated chemodynamic ferroptosis in T24 cells. We also manipulated the localized administration of Au@Chl-Fe combined with PDT at restricted regions in orthotopic tumor-bearing mice to cure malignant BC successfully without recurrence. By intravesical instillation of the Au@Chl/Fe-CPBA nanorods, this localized treatment could prevent the material from entering the systemic circulation, thus minimizing systemic toxicity. Upon activating NIR-PDT-elicited chemodynamic therapy, ultrasound imaging revealed almost complete tumor remission. Anti-tumor efficacy and survival benefit were achieved with a green photosensitizer.

Shape dependent photocatalytic H2 evolution of a zinc porphyrin

Hydrogen is regarded as a promising molecular fuel in order to produce clean energy, thus it is of great importance to produce and store H₂ in order to replace fossil fuels and to resolve the global energy and environmental problems. One strategy to produce hydrogen is the photocatalytic splitting of water. In this study different supramolecular architectures of a Zn(II) porphyrin, showing "flower", octahedral and "manta ray" shaped structures, were obtained using the "good-bad" solvent self-assembly protocol. More specifically, the bad solvent (methanol) was retained and the good solvent was alerted obtaining diverse assemblies. The different structures were studied by scanning electron microscopy, PXRD, UV-Vis and IR spectroscopies. The prepared structures were capable of proton reduction and production of molecular H₂ in the presence of 5% w/w Pt-nanoparticles as catalysts and ascorbic acid as a sacrificial electron donor. Moreover, depending on the structure of the chromophore that is formed the amount of H₂ produced varies. The maximum H₂ production was obtained with the octahedral structures (185.5 μmol g^-1 h^-1).

Regioisomer-Directed Self-Assembly of Alternating Copolymers for Highly Enhanced Photocatalytic H2 Evolution

Porphyrin-based photocatalytic materials have received great attention, and the effect of the substituents, central ions, and aggregated structure on the catalysis performance has been studied up to now. Herein, we report the effect of porphyrin isomerism on their aggregated structures as well as the photocatalytic activity. Two trans- and cis-porphyrin-based alternating copolymers with the same compositions (P1 and P2) are successfully synthesized. It is found that P1 self-assembles into propeller-like nanoparticles and P2 into multilayer hollow nanospheres. Furthermore, the hydrogen production rate of P1 (5533 μmol g^-1 h^-1) is 30 times higher than that of P2 (173 μmol g^-1 h^-1). Mechanism studies reveal that the high photocatalytic properties of P1 originate from the more ordered arrangement of porphyrins than P2, which facilitates the mobility and separation of photoinduced carriers. We believe the covalent and noncovalent polymer self-assembly process as well as the isomerism effect as disclosed here will shed new light on the design of high performance photocatalysts.

Adsorption of DNA Oligonucleotides by Self-Assembled Metalloporphyrin Nanomaterials

Porphyrin assemblies have controllable morphology, high biocompatibility, and good optical properties and were widely used in biomedical diagnosis and treatment. With the development of DNA biotechnology, combining DNA with porphyrin assemblies can broaden the biological applications of porphyrins. Porphyrin assemblies can serve as nanocarriers for DNA, although the fundamental interactions between them are not well understood. In this work, zinc meso-tetra(4-pyridyl)porphyrin (ZnTPyP) assemblies were prepared in the presence of various surfactants and at different pH values, yielding a variety of aggregation forms. Among them, the hexagonal stacking form exposes more pyridine substituents, and the hydrogen bonding force between the substituents and the DNA bases allows the DNA to be quickly adsorbed on the surface of the assemblies. The effects of DNA sequence and length were systematically tested. In particular, the adsorption of duplex DNA was less efficient compared to the adsorption of single-stranded DNA. This fundamental study is useful for the further combination of DNA and porphyrin assemblies to prepare new functional hybrid nanomaterials.

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.

Nanoscale self-assembly: concepts, applications and challenges

Self-assembly offers unique possibilities for fabricating nanostructures, with different morphologies and properties, typically from vapour or liquid phase precursors. Molecular units, nanoparticles, biological molecules and other discrete elements can spontaneously organise or form via interactions at the nanoscale. Currently, nanoscale self-assembly finds applications in a wide variety of areas including carbon nanomaterials and semiconductor nanowires, semiconductor heterojunctions and superlattices, the deposition of quantum dots, drug delivery, such as mRNA-based vaccines, and modern integrated circuits and nanoelectronics, to name a few. Recent advancements in drug delivery, silicon nanoelectronics, lasers and nanotechnology in general, owing to nanoscale self-assembly, coupled with its versatility, simplicity and scalability, have highlighted its importance and potential for fabricating more complex nanostructures with advanced functionalities in the future. This review aims to provide readers with concise information about the basic concepts of nanoscale self-assembly, its applications to date, and future outlook. First, an overview of various self-assembly techniques such as vapour deposition, colloidal growth, molecular self-assembly and directed self-assembly/hybrid approaches are discussed. Applications in diverse fields involving specific examples of nanoscale self-assembly then highlight the state of the art and finally, the future outlook for nanoscale self-assembly and potential for more complex nanomaterial assemblies in the future as technological functionality increases.

Graphene quantum dots-porphyrins/phthalocyanines multifunctional hybrid systems: from interfacial dialogue to applications

Engineered well-ordered hybrid nanomaterials are at a symbolically pivotal point, just ahead of a long-anticipated human race transformation. Incorporating newer carbon nanomaterials like graphene quantum dots (GQDs) with tetrapyrrolic porphyrins...

Construction of Interfacial Electric Field via Dual-Porphyrin Heterostructure Boosting Photocatalytic Hydrogen Evolution

A dual-porphyrin heterostructure is successfully constructed by coupling tetrakis (4-carboxyphenyl) zinc porphyrin (ZnTCPP) with tetrakis (4-hydroxyphenyl) porphyrin (THPP). The high photocatalytic H₂ evolution rate of 41.4 mmol h^-1 g^-1 is obtained for ZnTCPP/THPP under full spectrum, which is ≈5.1 and ≈17.0 times higher than that of pure ZnTCPP and THPP, respectively. The significantly enhanced activity is mainly attributed to the giant interfacial electric field formed between dual porphyrins, which greatly facilitates efficient charge separation and transfer. Meanwhile, similar conjugated structures of dual porphyrins also provide proper interface match and decrease interface defects, thus inhibiting the recombination of photoproduced carriers. By rationally combining the appropriate band structures and high-quality interfacial contact of dual porphyrins, this work provides a fresh insight into the interfacial electric field construction to improve the photocatalytic performance.

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.

Ultrafast Electron Transfer in a Self-Assembling Sulfonated Aluminum Corrole-Methylviologen Complex

Photoinduced electron transfer systems can mimic certain features of natural photosynthetic reaction centers, which are crucial for solar energy production. Among other tetra-pyrroles, the versatile chemical and photophysical properties of corroles make them very promising donors applicable in donor-acceptor complexes. Here, we present a first comprehensive study of ultrafast photoinduced electron transfer in a self-assembling sulfonated aluminum corrole-methylviologen complex combining visible and mid-IR transient absorption spectroscopy. The noncovalent D-A association of the corrole-methylviologen complex has the great advantage that photoinduced charge separation becomes possible even though the back electron transfer (BET) rate is large. Initial forward electron transfer from corrole to methylviologen is observed on an ∼130 fs time scale. Subsequent back electron transfer takes place with τ_BET = (1.8 ± 0.5) ps, revealing very complex relaxation dynamics. Direct probing in the mid-IR allows us to unravel the back electron transfer and cooling dynamics/electronic reorganization. Upon tracing the dynamics of the methylviologen-radical marker band at 1640 cm^-1 and the C═C stretching of corrole at around 1500 cm^-1, we observe that large amounts of excess energy survive the back transfer, leading to the formation of hot ground state absorption. A closer examination of the signal after 300 ps, surviving the back transfer, exhibits a charge-separation yield of 10-15%.

Self-Assembly of Porphyrin Nanofibers on ZnO Nanoparticles for the Enhanced Photocatalytic Performance for Organic Dye Degradation

Synthesizing novel photocatalysts that can effectively harvest photon energy over a wide range of the solar spectrum for practical applications is vital. Porphyrin-derived nanostructures with properties similar to those of chlorophyll have emerged as promising candidates to meet this requirement. In this study, tetrakis(4-carboxyphenyl) porphyrin (TCPP) nanofibers were formed on the surface of ZnO nanoparticles using a simple self-assembly approach. The obtained ZnO/TCPP nanofiber composites were characterized via scanning electron microscopy, X-ray diffraction analysis, and ultraviolet-visible absorbance and reflectance measurements. The results demonstrated that the ZnO nanoparticles with an average size of approximately 37 nm were well integrated in the TCPP nanofiber matrix. The resultant composite showed photocatalytic activity of ZnO and TCPP nanofibers concomitantly, with band gap energies of 3.12 and 2.43 eV, respectively. The ZnO/TCPP photocatalyst exhibited remarkable photocatalytic performance for RhB degradation with a removal percentage of 97% after 180 min of irradiation under simulated sunlight because of the synergetic activity of ZnO and TCPP nanofibers. The dominant active species participating in the photocatalytic reaction were •O2 - and OH•, resulting in enhanced charge separation by exciton-coupled charge-transfer processes between the hybrid materials.

A Superficial Intramolecular Alignment of Carbon Nitride through Conjugated Monomer for Optimized Photocatalytic CO2 Reduction

One of the most frequent ways to widen the adsorption range of carbon nitride (CN) is to add a well-known photosensitizer into its basic structure. So far, such attachments have been accomplished by using weak van der Waals forces. However, using strong covalent bonding to attach such photosensitizer with CN is yet to be determined. Here, for the first time, we covalently bonded porphyrin (5,10,15,20-tetrakis(4-(2,4-diamino-1,3,5-triazinyl) phenyl)-Porphyrin (TDP)), a renowned photosensitizer, effectively with CN by thermally balanced molecular strategy. A photoreaction system was set up for the deoxygenated conversion of CO2 to CO under visible light, where cobalt acted as a redox controller to speed up the charge transportation, while CN-TDP worked as a CO2 activating photocatalyst. The subsequent photocatalyst has a broader absorbance range, a greater specific surface area, and intramolecular organic connections that help to decrease the electron-hole pairs’ recombination rate. Furthermore, the average weight ratio between urea and TDP was well-tuned, resulting in a fantastic CO2 photoconversion for CN-TDP7.0 compared to the blank sample. This substantial increase in photocatalytic activity predicts a significant shift in CN’s specific surface area, band gap, chemical composition, and structure, as well as the efficient separation of photogenerated charge carriers from the ground state (HOMO) to the excited state (LUMO), making it a top candidate for CO2 photoreduction. At the same time, this approach paves the path for the bottom-up fabrication of carbon nitride nanosheets.

Protein-aggregating ability of different protoporphyrin-IX nanostructures is dependent on their oxidation and protein-binding capacity

Porphyrias are rare blood disorders caused by genetic defects in the heme biosynthetic pathway and are associated with the accumulation of high levels of porphyrins that become cytotoxic. Porphyrins, due to their amphipathic nature, spontaneously associate into different nanostructures, but very little is known about the cytotoxic effects of these porphyrin nanostructures. Previously, we demonstrated the unique ability of fluorescent biological porphyrins, including protoporphyrin-IX (PP-IX), to cause organelle-selective protein aggregation, which we posited to be a major mechanism by which fluorescent porphyrins exerts their cytotoxic effect. Herein, we tested the hypothesis that PP-IX-mediated protein aggregation is modulated by different PP-IX nanostructures via a mechanism that depends on their oxidizing potential and protein-binding ability. UV–visible spectrophotometry showed pH-mediated reversible transformations of PP-IX nanostructures. Biochemical analysis showed that PP-IX nanostructure size modulated PP-IX-induced protein oxidation and protein aggregation. Furthermore, albumin, the most abundant serum protein, preferentially binds PP-IX dimers and enhances their oxidizing ability. PP-IX binding quenched albumin intrinsic fluorescence and oxidized His-91 residue to Asn/Asp, likely via a previously described photo-oxidation mechanism for other proteins. Extracellular albumin protected from intracellular porphyrinogenic stress and protein aggregation by acting as a PP-IX sponge. This work highlights the importance of PP-IX nanostructures in the context of porphyrias and offers insights into potential novel therapeutic approaches.

Photocatalytic hydrogen production of porphyrin nanostructures: spheres vs. fibrils, a case study

Herein, we illustrate the preparation of a covalent connected peptide-porphyrin hybrid (Fmoc-FF-(Zn)Por). The thorough investigation of its self-organization features demonstrated that Fmoc-FF-(Zn)Por self-assembles into either spheres or fibrils by altering the solvent mixture. Interestingly, photocatalytic hydrogen (H2) evolution experiments revealed that fibrils were more efficient towards H2 production compared to spheres.

Surfactant-Induced Interfacial Aggregation of Porphyrins for Structuring Color-Tunable Liquids

Locking nonequilibrium shapes of liquids into targeted architectures by interfacial jamming of nanoparticles is an emerging area in material science. 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (H₆ TPPS) shows three different aggregation states that present an absorption imaging platform to monitor the assembly and jamming of supramolecular polymer surfactants (SPSs) at the liquid/liquid interface. The interfacial interconversion of H₆ TPPS, specifically H₄ TPPS^2- dissolved in water, from J- to an H-aggregation was induced by strong electrostatic interactions with amine-terminated polystyrene dissolved in toluene at the water/toluene interface. This resulted in color-tunable liquids due to interfacial jamming of the SPSs formed between H₄ TPPS^2- and amine-terminated polystyrene. However, the formed SPSs cannot lock in nonequilibrium shapes of liquids. In addition, a self-wrinkling behavior was observed when amphiphilic triblock copolymers of PS-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) were used to interact with H₄ TPPS^2- . Subsequently, the SPSs formed can lock in nonequilibrium shapes of liquids.

Boosting photocatalytic hydrogen production activity by a microporous II nanoribbon decorated with Pt nanoparticles

Due to the synergistic effect between photoactive Cu^II and Pt sites, the Pt(4.38 wt%)/Cu^II-MOF nanoribbon exhibits an enhanced hydrogen production rate, obviously higher by 4.7 and 1.9 times than those of the individual Pt nanoparticle and Cu^II-MOF.

Porphyrin metalation catalyzed by DNAzymes and nanozymes

In this review, DNA and nanomaterial based catalysts for porphyrin metalation reactions are summarized, including the selection of DNAzymes, choice of nanomaterials, their catalytic mechanisms, and applications of the reactions.

Synthesis of novel porphyrin derivatives and their self-assemblies to enhance photocatalytic performance

Preparation of new porphyrin derivatives and their self-assemblies to improve photocatalytic performance.