Morphology-controlled self-assembly and synthesis of photocatalytic nanocrystals

Controlled nanocrystallization of gold nanoclusters within surfactant envelopes: enhancing aggregation-induced emission in solution

The nanocrystallization of functional molecules has been a subject of recent interest in the current development of nanotechnology. Herein, we report the unprecedented synthesis of single nanocrystals of a molecular gold nanocluster in a homogeneous solution by using surfactant-based nano-envelopes. The co-assembling of a Au8 nanocluster carrying lipophilic phosphine ligands with sodium dodecyl sulfate (SDS) in an aqueous solution results in the formation of sphere-shaped amorphous nano-aggregates coated with the surfactant. Upon sonication, the spherical amorphous aggregates are smoothly shape-shifted into discrete rhombic nanocrystals, which can be tracked by TEM and solution XRD. The transformation into single nanocrystals occurs exclusively without further growth or agglomeration, implying that the crystal growth is restricted within the surfactant nano-envelopes. The robust but flexible nature of the wrapped surfactant is likely responsible for the controlled crystallization. We also demonstrate that the amorphous-to-nanocrystalline transition in solution remarkably enhances the photoluminescence emission from the nanocluster, providing a clear example of crystallization-induced emission enhancement. Notably, the obtained nanocrystals showed high stability in solution and retained their shape, size, and PL intensity even after several months, owing to the densely packed surfactant shell. The present surfactant-directed nanocrystallization method may be applicable to other molecular species to contribute to the development of nanocluster science as well as the designed synthesis of nanomaterials.

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.

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.

Microemulsion-Assisted Self-Assembly of Indium Porphyrin Photosensitizers with Enhanced Photodynamic Therapy

Designing and constructing supramolecular photosensitizer nanosystems with highly efficient photodynamic therapy (PDT) is vital in the nanomedical field. Despite recent advances in forming well-defined superstructures, the relationship between molecular arrangement in nanostructures and photodynamic properties has rarely been involved, which is crucial for developing stable photosensitizers for highly efficient PDT. In this work, through a microemulsion-assisted self-assembly approach, indium porphyrin (InTPP) was used to fabricate a series of morphology-controlled self-assemblies, including nanorods, nanospheres, nanoplates, and nanoparticles. They possessed structure-dependent 1O2 generation efficiency. Compared with the other three nanostructures, InTPP nanorods featuring strong π-π stacking, J-aggregation, and high crystallinity proved to be much more efficient at singlet oxygen (1O2) production. Also, theoretical modeling and photophysical experiments verified that the intermolecular π-π stacking in the nanorods could cause a decreased singlet-triplet energy gap (ΔEST) compared with the monomer. This played a key role in enhancing intersystem crossing and facilitating 1O2 generation. Both in vitro and in vivo experiments demonstrated that the InTPP nanorods could trigger cell apoptosis and tumor ablation upon laser irradiation (635 nm, 0.1 W/cm2) and exhibited negligible dark toxicity and high phototoxicity. Thus, the supramolecular self-assembly strategy provides an avenue for designing high-performance photosensitizer nanosystems for photodynamic therapy and beyond.

Adsorption and photocatalytic applications of porphyrin-based materials for environmental separation processes: A review

As society progresses and industrializes, the issue of water pollution, caused by a wide array of organic and inorganic pollutants, poses significant risks to both human well-being and the environment. Given its distinctive characteristics, water pollution has become a paramount concern for society, necessitating immediate attention. Numerous studies have been conducted on wastewater treatment, primarily focusing on two key approaches: adsorption and photocatalytic degradation. Adsorption offers unparalleled advantages, including its simplicity, high removal efficiency, and cost-effectiveness. Conversely, photocatalysis harnesses abundant, clean, and non-polluting sunlight, addressing the critical issue of energy scarcity. Porphyrins, which are macrocyclic tetrapyrrole derivatives found widely in nature, have attracted growing interest in recent years. These lipophilic pigments exhibit remarkable chemical stability and have retained their major structural features for up to 1.1 billion years. As such, they are considered vital indicators of life and have been extensively studied, from the remnants of extinct organisms to gain insights into the principles of evolution. Porphyrins are often associated with a central metal ion within their ring system and can be modified through various substituents, including additional rings or ring opening, resulting in a wide range of functionalities. This comprehensive review summarizes recent advancements in the field of porphyrins. It begins by introducing the structures and preparation methods of porphyrins. Subsequently, it delves into notable applications of porphyrins in the context of pollutant adsorption in water and their environmentally friendly photocatalytic degradation.

Next Generation Gold Drugs and Probes: Chemistry and Biomedical Applications

The gold drugs, gold sodium thiomalate (Myocrisin), aurothioglucose (Solganal), and the orally administered auranofin (Ridaura), are utilized in modern medicine for the treatment of inflammatory arthritis including rheumatoid and juvenile arthritis; however, new gold agents have been slow to enter the clinic. Repurposing of auranofin in different disease indications such as cancer, parasitic, and microbial infections in the clinic has provided impetus for the development of new gold complexes for biomedical applications based on unique mechanistic insights differentiated from auranofin. Various chemical methods for the preparation of physiologically stable gold complexes and associated mechanisms have been explored in biomedicine such as therapeutics or chemical probes. In this Review, we discuss the chemistry of next generation gold drugs, which encompasses oxidation states, geometry, ligands, coordination, and organometallic compounds for infectious diseases, cancer, inflammation, and as tools for chemical biology via gold-protein interactions. We will focus on the development of gold agents in biomedicine within the past decade. The Review provides readers with an accessible overview of the utility, development, and mechanism of action of gold-based small molecules to establish context and basis for the thriving resurgence of gold in medicine.

Porphyrin-Based Covalent Organic Frameworks: Design, Synthesis, Photoelectric Conversion Mechanism, and Applications

Photosynthesis occurs in high plants, and certain organisms show brilliant technology in converting solar light to chemical energy and producing carbohydrates from carbon dioxide (CO₂). Mimicking the mechanism of natural photosynthesis is receiving wide-ranging attention for the development of novel materials capable of photo-to-electric, photo-to-chemical, and photocatalytic transformations. Porphyrin, possessing a similar highly conjugated core ring structure to chlorophyll and flexible physical and chemical properties, has become one of the most investigated photosensitizers. Chemical modification and self-assembly of molecules as well as constructing porphyrin-based metal (covalent) organic frameworks are often used to improve its solar light utilization and electron transfer rate. Especially porphyrin-based covalent organic frameworks (COFs) in which porphyrin molecules are connected by covalent bonds combine the structural advantages of organic frameworks with light-capturing properties of porphyrins and exhibit great potential in light-responsive materials. Porphyrin-based COFs are expected to have high solar light utilization, fast charge separation/transfer performance, excellent structural stability, and novel steric selectivity by special molecular design. In this paper, we reviewed the research progress of porphyrin-based COFs in the design, synthesis, properties, and applications. We focused on the intrinsic relationship between the structure and properties, especially the photoelectric conversion properties and charge transfer mechanism of porphyrin-based COFs, and tried to provide more valuable information for the design of advanced photosensitizers. The applications of porphyrin-based COFs in photocatalysis and phototherapy were emphasized based on their special structure design and light-to-electric (or light-to-heat) conversion control.

Heterophase Polymorph of TiO2 (Anatase, Rutile, Brookite, TiO2 (B)) for Efficient Photocatalyst: Fabrication and Activity

TiO2 exists naturally in three crystalline forms: Anatase, rutile, brookite, and TiO2 (B). These polymorphs exhibit different properties and consequently different photocatalytic performances. This paper aims to clarify the differences between titanium dioxide polymorphs, and the differences in homophase, biphase, and triphase properties in various photocatalytic applications. However, homophase TiO2 has various disadvantages such as high recombination rates and low adsorption capacity. Meanwhile, TiO2 heterophase can effectively stimulate electron transfer from one phase to another causing superior photocatalytic performance. Various studies have reported the biphase of polymorph TiO2 such as anatase/rutile, anatase/brookite, rutile/brookite, and anatase/TiO2 (B). In addition, this paper also presents the triphase of the TiO2 polymorph. This review is mainly focused on information regarding the heterophase of the TiO2 polymorph, fabrication of heterophase synthesis, and its application as a photocatalyst.

Synthesis of the ZnTPyP/WO3 nanorod-on-nanorod heterojunction direct Z-scheme with spatial charge separation ability for enhanced photocatalytic hydrogen generation

The direct Z-scheme photocatalytic system can effectively improve the separation efficiency of photogenerated carriers through the photosynthesis-based photocarrier transport model. In this study, zinc porphyrin-assembled nanorods (ZnTPyP) and WO₃ nanorods' nanorod-on-nanorod heterojunctions (ZnTPyP/WO₃) were successfully prepared through a simple modified acid-base neutralization micelle-confined assembly method using WO₃ nanorods as the nucleation template and ZnTPyP as building blocks. ZnTPyP achieved a controllable assembly onto WO₃ nanorods through N-W coordination. ZnTPyP/WO₃ nanorod-on-nanorod heterojunctions exhibited a structure-dependent photocatalytic performance for hydrogen production. The ZnTPyP/WO₃ nanorod-on-nanorod heterojunctions exhibited a optimal hydrogen production rate (74.53 mmol g^-1 h^-1) using Pt as the co-catalyst, which was 2.64 times that of the ZnTPyP self-assembled nanorods. The improvement in the photocatalytic hydrogen production efficiency could be mainly attributed to the direct Z-scheme electron-transfer mechanism from WO₃ to ZnTPyP. This is the first report of an approach using porphyrin-assembled nanostructures to construct organic-inorganic Z-scheme photocatalysts. This study offers valuable information for preparing new efficient photocatalysts based on organic supramolecular orderly aggregate materials.

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.

Zn (II)-porphyrin-based photochemically green synthesis of novel ZnTPP/Cu nanocomposites with antibacterial activities and cytotoxic features against breast cancer cells

This study focuses on synthesizing novel nanocomposites, zinc(II)tetrakis(4-phenyl)porphyrin/Cu nanoparticles (ZnTPP/Cu-NPs),with antibacterial activity, fabricated through a single-step green procedure. In this regard, the self-assembly of ZnTPP was carried out through an acid-base neutralization method to prepare ZnTPP nanoparticles. Then, the copper nanoparticles (Cu-NPs) were grown on ZnTPP nanoparticles through a visible-light irradiated photochemical procedure in the absence and presence of polyacrylic acid (PAA) as a modulator. The effect of PAA on the morphological properties of the prepared nanocomposites was evaluated. Eventually, the antibacterial activity of nanocomposites with different morphologies was investigated. In this way, the average zone of inhibition growth of diameter, minimum inhibitory concentration, and minimum bactericidal concentration values was determined. Besides, the cytotoxicity of the nanocomposites was evaluated by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay MCF-7and (HEK-293) cell lines. The specific features of the synthesized nanocomposites identified them as antibacterial compounds which have therapeutic effects on breast cancer.

Fluorescence Biosensor for One-Step Simultaneous Detection of Mycobacterium tuberculosis Multidrug-Resistant Genes Using nanoCoTPyP and Double Quantum Dots

The diagnosis of multidrug-resistant tuberculosis (MDR-TB) is crucial for the subsequent drug guidance to improve therapy and control the spread of this infectious disease. Herein, we developed a novel florescence biosensor for simultaneous detection of Mycobacterium tuberculosis (Mtb) multidrug-resistant genes (rpoB531 for rifampicin and katG315 for isoniazid) by using our synthesized nanocobalt 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (nanoCoTPyP) and double quantum dots (QDs). Several nanoCoTPyPs with different charges and morphology were successfully prepared via the surfactant-assisted method and their quenching ability and restoring efficiency for DNA detection were systematically analyzed. It was found that spherical nanoCoTPyP with positive charge exhibited excellent quenching effect and sensing performance for the two DNAs' detection due to its affinity differences towards single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). ssDNA attached on QDs (QDs-ssDNA) was specifically hybridized with targets to form QDs-dsDNA, resulting in fluorescence recovery due to the disruption of the interactions between nanoCoTPyP and ssDNA. Two drug-resistant genes could be simultaneously quantified in a single run and relatively low limits of detection (LODs) were obtained (24 pM for T1 and 20 pM for T2). Furthermore, the accuracy and reliability of our method were verified by testing clinical samples. This simple and low-cost approach had great potential to be applied in clinical diagnosis of MDR-TB.

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.

Bi nanosphere-decorated oxygen-vacancy BiOBr hollow microspheres with exposed (110) facets to enhance the photocatalytic performance for the degradation of azo dyes

A facile preparation strategy is proposed for a novel highly-active composite photocatalyst comprising Bi nanosphere-decorated oxygen-vacancy BiOBr hollow microspheres with exposed (110) facets for the efficient degradation of azo dyes.

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.

Bismuth Vacancy-Induced Efficient CO2 Photoreduction in BiOCl Directly from Natural Air: A Progressive Step toward Photosynthesis in Nature

Photocatalytic CO₂ conversion into carbonaceous fuels through artificial photosynthesis is beneficial to global warming mitigation and renewable resource generation. However, a high cost is always required by special CO₂-capturing devices for efficient artificial photosynthesis. For achieving highly efficient photocatalytic CO₂ reduction (PCR) directly from natural air, we report rose-like BiOCl that is rich in Bi vacancies (V_Bi) assembled by nanosheets with almost fully exposed active {001} facets. These rose-like BiOCl with V_Bi assemblies provide considerable adsorption and catalytic sites, which hoists the CO₂ capture and reduction capabilities, and thus expedites the PCR to a superior value of 21.99 μmol·g^-1·h^-1 CO generation under a 300 W Xe lamp within 5 h from natural air. The novel design and construction of a photocatalyst in this work could break through the conventional PCR system requiring compression and purification for CO₂, dramatically reduce expenses, and open up new possibilities for the practical application of artificial photosynthesis.

Recent advances in assembled AIEgens for image-guided anticancer therapy

Image-guided therapy, with simultaneous imaging and therapy functions, has the potential to greatly enhance the therapeutic efficacy of anticancer therapy, and reduce the incidence of side effects. Fluorescence imaging has the advantages of easy operation, abundant signal, high contrast, and fast response for real-time and non-invasive tracking. Luminogens with aggregation-induced emission characteristics (AIEgens) can emit strong luminescence in an aggregate state, which makes them ideal materials to construct applicative fluorophores for fluorescence imaging. The opportunity for image-guided cancer treatment has inspired researchers to explore the theranostic application of AIEgens combined with other therapy methods. In recent years, many AIEgens with efficient photosensitizing or photothermal abilities have been designed by precise molecular engineering, with superior performance in image-guided anticancer therapy. Owing to the hydrophobic property of most AIEgens, an assembly approach has been wildly utilized to construct biocompatible AIEgen-based nanostructures in aqueous systems, which can be used for image-guided anticancer therapy. In the present review, we summarize the recent advances in the assembled AIEgens for image-guided anticancer therapy. Five types of image-guided anticancer therapy using assembled AIEgens are included: chemotherapy, photodynamic therapy, photothermal therapy, gene therapy, and synergistic therapy. Moreover, a brief conclusion with the discussion of current challenges and future perspectives in this area is further presented.

Porphyrin-based MOFs as heterogeneous photocatalysts for the eradication of organic pollutants and toxins

Water and air pollution are among the major environmental challenges of this era. Waste management, economic sustainable development and renewable energy are unavoidable concomitant considerations. Over the past five years, nanosized metal-organic frameworks (nano-MOFs) have been developed for the elimination of pollutants in wet media and air-born toxins using the highly efficient reactive oxygen species (ROS) of type I (H2O2, •OH, O[Formula: see text] and of type II (1O[Formula: see text]. The ROS are catalytically and efficiently generated through photosensitization, and porphyrins and metalloporphyrins are pigments of choice for this purpose. This short review summarizes the fundamentals of ROS generation by porphyrin-based nano-MOFs (mainly through the formation of ROS type II) and their composites (leading to ROS type I), which includes energy and electron transfer processes, and their applications in these environmental issues.

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.

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.

Aggregation-induced photocatalytic activity and efficient photocatalytic hydrogen evolution of amphiphilic rhodamines in water

The development of photocatalysts is an essential task for clean energy generation and establishing a sustainable society. This paper describes the aggregation-induced photocatalytic activity (AI-PCA) of amphiphilic rhodamines and photocatalytic functions of the supramolecular assemblies. The supramolecular assemblies consisting of amphiphilic rhodamines with octadecyl alkyl chains exhibited significant photocatalytic activity under visible light irradiation in water, while the corresponding monomeric rhodamines did not exhibit photocatalytic activity. The studies on the photocatalytic mechanism by spectroscopic and microscopic analyses clearly demonstrated the AI-PCA of the rhodamines. Moreover, the supramolecular assemblies of the rhodamines exhibited excellent photocatalytic hydrogen evolution rates (up to 5.9 mmol g-1 h-1).

Investigation of Morphology-Controlled Ultrafast Relaxation Processes of Aggregated Porphyrin

Here, we have synthesized rod and flake shaped morphology of porphyrin aggregates from 5, 10, 15, 20-tetra (4-n-octyloxyphenyl) porphyrin (4-opTPP) molecule which are evident from scanning electron microscopy (SEM). The formation of J-type aggregation is evident from steady state and time-resolved fluorescence spectroscopic studies. Ultrafast transient absorption spectroscopic studies reveal that the excited state lifetime is controlled by the morphology and the time constant for S₁→S₀ relaxation changes from 3.05 ps to 744 ps with changing the shape from rod to flake, respectively. In spite of similar exciton coupling energy in both the aggregates, the flake shaped aggregates undergo a faster exciton relaxation process and the non-radiative relaxation channels are found to depend on the shape of aggregates. The fundamental understanding of morphology controlled ultrafast relaxation processes of aggregated porphyrin is important for designing efficient light harvesting devices.

Self-assembly of anisotropic nanoparticles into functional superstructures

Self-assembly of colloidal nanoparticles (NPs) into superstructures offers a flexible and promising pathway to manipulate the nanometer-sized particles and thus make full use of their unique properties. This bottom-up strategy builds a bridge between the NP regime and a new class of transformative materials across multiple length scales for technological applications. In this field, anisotropic NPs with size- and shape-dependent physical properties as self-assembly building blocks have long fascinated scientists. Self-assembly of anisotropic NPs not only opens up exciting opportunities to engineer a variety of intriguing and complex superlattice architectures, but also provides access to discover emergent collective properties that stem from their ordered arrangement. Thus, this has stimulated enormous research interests in both fundamental science and technological applications. This present review comprehensively summarizes the latest advances in this area, and highlights their rich packing behaviors from the viewpoint of NP shape. We provide the basics of the experimental techniques to produce NP superstructures and structural characterization tools, and detail the delicate assembled structures. Then the current understanding of the assembly dynamics is discussed with the assistance of in situ studies, followed by emergent collective properties from these NP assemblies. Finally, we end this article with the remaining challenges and outlook, hoping to encourage further research in this field.

Pre-Polymerization Enables Controllable Synthesis of Nanosheet-Based Porphyrin Polymers towards High-Performance Li-Ion Batteries

The precise regulation of nucleation growth and assembly of polymers is still an intriguing goal but an enormous challenge. In this study, we proposed a pre-polymerization strategy to regulate the assembly and growth of polymers by facilely controlling the concentration of polymerization initiator, and thus obtained two kinds of different nanosheet-based porphyrin polymer materials using tetrakis-5,10,15,20-(4-aminophenyl) porphyrin (TAPP) as the precursor. Notably, due to the π-π stacking and doping of TAPP during the preparation process, the obtained PTAPP-nanocube material exhibits a high intrinsic bulk conductivity reaching 1.49×10^-4  S m^-1 . Profiting from the large π-conjugated structure of porphyrin units, closely stacked layer structure and excellent conductivity, the resultant porphyrin polymers, as electrode materials for lithium ion batteries, deliver high specific capacity (≈650 mAh g^-1 at the current density of 100 mA g^-1 ), excellent rate performance and long-cycle stability, which are among the best reports of porphyrin polymer-based electrode materials for lithium-ion batteries, to the best of our knowledge. Therefore, such a pre-polymerization approach would provide a new insight for the controllable synthesis of polymers towards custom-made architecture and function.

The formation mechanism of ZnTPyP fibers fabricated by a surfactant-assisted method

Zn–N coordination and the sphere-to-rod transition of CTAB micelles contribute concertedly to the formation of ZnTPyP fibers.

Tuning the Supramolecular Structures of Metal-Free Porphyrin via Surfactant Assisted Self-Assembly to Enhance Photocatalytic Performance

Metal-free porphyrin with good planarity is beneficial to π-π stack interactions, which promotes electron coupling and the separation and transfer of photogenerated carriers. It is necessary to develop metal-free porphyrin-based photocatalysts and exploit the photocatalytic mechanism. Herein, metal-free porphyrin (5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, TCPP) was self-assembled through an acid-based neutralization reaction and mixing dual-solvents under surfactants to form different aggregates. Morphology structures, optical and optoelectronic properties of the TCPP aggregates were characterized in detail. TCPP self-assemblies showed higher photocatalytic activities for the degradation of phenol under visible light than untreated TCPP powders, and the aggregates of nanorods formed through the acid-based neutralization reaction in the presence of hexadecyl trimethyl ammonium bromide (CTAB) possessed 2.6 times more activity than the nanofiber aggregates formed through mixing dual-solvents. It was proved that self-assembly methods are crucial for controlling the aggregation of porphyrins to form different aggregations, which have a profound impact on the photocatalytic activity.

Pressure Induced Nanoparticle Phase Behavior, Property, and Applications

Nanoparticle (NP) high pressure behavior has been extensively studied over the years. In this review, we summarize recent progress on the studies of pressure induced NP phase behavior, property, and applications. This review starts with a brief overview of high pressure characterization techniques, coupled with synchrotron X-ray scattering, Raman, fluorescence, and absorption. Then, we survey the pressure induced phase transition of NP atomic crystal structure including size dependent phase transition, amorphization, and threshold pressures using several typical NP material systems as examples. Next, we discuss the pressure induced phase transition of NP mesoscale structures including topics on pressure induced interparticle separation distance, NP coupling, and NP coalescence. Pressure induced new properties and applications in different NP systems are highlighted. Finally, outlooks with future directions are discussed.

Control of post-growth processes for the selection of metallo-tetraphenylporphyrin nanowires

Controlling self-organization of small organic molecules in nanostructures with a desired shape and size is one of the main challenges in organic nanoelectronics. Here, a strategy for selectively growing uniaxially aligned nanowires of meso-tetraphenyl porphyrin-Zn(ii) (ZnTPP) is presented. ZnTPP is deposited on an organic single crystal, namely potassium hydrogen phthalate, by organic molecular beam epitaxy. The films typically display a rather rich surface morphology, characterized by the presence of nanowires and other nm-sized aggregates, most of them unstable over time. Post-growth processes occurring via quasi-Ostwald ripening both in air and in vacuum demonstrate an aging protocol in vacuum as a tool for the selection of ZnTPP nanowires, whose morphology and uniaxial orientation are demonstrated to be led by organic epitaxy. The ability of growing ZnTPP nanowires with a unique crystal structure and precise orientation gives the chance to observe the intrinsic optical anisotropy of the triclinic polymorph of ZnTPP crystal and establishes the role of intermolecular interactions, providing new perspectives in the study of the intrinsic physical properties of ZnTPP crystals.

Microemulsion-Assisted Self-Assembly and Synthesis of Size-Controlled Porphyrin Nanocrystals with Enhanced Photocatalytic Hydrogen Evolution

Design and engineering of highly efficient light-harvesting nanomaterial systems to emulate natural photosynthesis for maximizing energy conversion have stimulated extensive efforts. Here we present a new class of photoactive semiconductor nanocrystals that exhibit high-efficiency energy transfer for enhanced photocatalytic hydrogen production under visible light. These nanocrystals are formed through noncovalent self-assembly of In(III) meso-tetraphenylporphine chloride (InTPP) during microemulsion assisted nucleation and growth process. Through kinetic control, a series of uniform nanorods with controlled aspect ratio and high crystallinity have been fabricated. Self-assembly of InTPP porphyrins results in extensive optical coupling and broader coverage of the visible spectrum for efficient light harvesting. As a result, these nanocrystals display excellent photocatalytic hydrogen production and photostability under the visible light in comparison with the commercial InTPP porphyrin powders.

Surfactant-Assisted Cooperative Self-Assembly of Nanoparticles into Active Nanostructures

Nanoparticles (NPs) of controlled size, shape, and composition are important building blocks for the next generation of devices. There are numerous recent examples of organizing uniformly sized NPs into ordered arrays or superstructures in processes such as solvent evaporation, heterogeneous solution assembly, Langmuir-Blodgett receptor-ligand interactions, and layer-by-layer assembly. This review summarizes recent progress in the development of surfactant-assisted cooperative self-assembly method using amphiphilic surfactants and NPs to synthesize new classes of highly ordered active nanostructures. Driven by cooperative interparticle interactions, surfactant-assisted NP nucleation and growth results in optically and electrically active nanomaterials with hierarchical structure and function. How the approach works with nanoscale materials of different dimensions into active nanostructures is discussed in details. Some applications of these self-assembled nanostructures in the areas of nanoelectronics, photocatalysis, and biomedicine are highlighted. Finally, we conclude with the current research progress and perspectives on the challenges and some future directions.

Uniform zinc thioporphyrazine nanosphere by self-assembly and the photocatalytic performance

A novel strategy for the synthesis of zinc thioporphyrazine nanospheres is presented. The uniform spheres were fabricated through a polymerization reaction without using any template or emulsifier, which result from the covalent links between zinc tetra(2,3-bis(pentenylthio)porphyrazine (ZnPz) possessing eight long flexible chains in periphery and each with one terminal olefin group. A possible mechanism to explain the self-assembly of ZnPz nanospheres was also illuminated through monitoring nanosphere formation by means of transmission electron microscopy (TEM). More importantly, ZnPz nanospheres can effectively activate dioxygen in aqueous media under simulated sunlight irradiation, and showed significantly improved photocatalytic activity for the degradation of Rhodamine B (RhB) as compared to monomeric ZnPz. Furthermore, the reactive oxygen species derived from ZnPz nanospheres under light irradiation were determined by electron paramagnetic resonance (EPR) technology, indicating that singlet oxygen ([Formula: see text]O[Formula: see text] and hydroxyl radical (•OH) are the major reactive oxygen species. The facile synthetic methodology and the enhanced photocatalytic performance of the ZnPz nanospheres endow this novel material with the potential of being an efficient biomimetic photocatalyst for wastewater treatment.

Colloid-Interface-Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities

High-efficient charge and energy transfer between nanocrystals (NCs) in a bottom-up assembly are hard to achieve, resulting in an obstacle in application. Instead of the ligands exchange strategies, the advantage of a continuous laser is taken with optimal wavelength and power to irradiate the film-scale NCs superlattices at solid-liquid interfaces. Owing to the Au-based NCs' surface plasmon resonance (SPR) effect, the gentle laser irradiation leads the Au NCs or Au@CdS core/shell NCs to attach each other with controlled pattern at the interfaces between solid NCs phase and liquid ethanol/ethylene glycol. A continuous wave 532 nm laser (6.68-13.37 W cm^-2 ), to control Au-based superlattices, is used to form the monolayer with uniformly reduced interparticle distance followed by welded superstructures. Considering the size effect to Au NCs' melting, when decreasing the Au NCs size to ≈5 nm, stronger welding nanostructures are obtained with diverse unprecedented shapes which cannot be achieved by normal colloidal synthesis. With the help of facile scale-up and formation at solid-liquid interfaces, and a good connection of crystalline between NCs, the obtained plasmonic superstructured films that could be facilely transferred onto different substrates exhibit broad SPR absorption in the visible and near-infrared regime, enhanced electric conductivities, and wide applications as surface enhanced Raman scattering (SERS)-active substrates.

Photoelectron Transfer at ZnTPyP Self-Assembly/TiO2 Interfaces for Enhanced Two-Photon Photodynamic Therapy

Two-photon (TP) absorption nanomaterials are highly desirable for deep-tissue clinical diagnostics and orthotopic disease treatment. Here, a well-designed core/shell nanostructure was successfully synthesized with a ZnTPyP self-assembly nanocrystal (ZSN) inner core coated by a homogeneous TiO₂ layer outside (ZSN-TO). The ZSN is a good photosemiconductor, showing both one-photon (OP) and TP absorption properties for red fluorescence emission and electron-hole pair generation; TiO₂ with good biocompatibility acts as the electron acceptor, which can transfer photoelectron from ZSN to TiO₂ for highly effective electron-hole separation, favoring the production of long-life superoxide anion (O₂^•-) by electrons and oxygen and strong oxidizing hydroxyl radical (•OH) by holes and surrounding H₂O. Once pretreated with ZSN-TO, the simultaneous OP-405 nm or TP-800 nm laser stimulation and fluorescent imaging of reactive oxygen species (ROS) showed dynamical and continuous generation of ROS in HeLa cells, with cytotoxicity significantly increasing via the type-1-like photodynamic therapy process. The results demonstrated that the combination of organic ZSN with inorganic TiO₂ has great applications as an excellent photosensitizer for deep-tissue fluorescent imaging and noninvasive disease treatment via TP photodynamic therapy.

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

There has been a widespread interest in the preparation of self-assembled porphyrin nanostructures and their ordered arrays, aiming to emulate natural light harvesting processes and energy storage and to develop new nanostructured materials for photocatalytic process. Here, we report controlled synthesis of one-dimensional porphyrin nanostructures such as nanorods and nanowires with well-defined self-assembled porphyrin networks that enable efficient energy transfer for enhanced photocatalytic activity in hydrogen generation. Preparation of these one-dimensional nanostructures is conducted through noncovalent self-assembly of porphyrins confined within surfactant micelles. X-ray diffraction and transmission electron microscopy results reveal that these one-dimensional nanostructures contain stable single crystalline structures with controlled interplanar separation distance. Optical absorption characterizations show that the self-assembly enables effective optical coupling of porphyrins, resulting in much more enhanced optical absorption in comparison with the original porphyrin monomers, and the absorption bands red shift to more extensive visible light spectrum. The self-assembled porphyrin network facilitates efficient energy transfer among porphyrin molecules and the delocalization of excited state electrons for enhanced photocatalytic hydrogen production under visible light.

Photocatalyst with annulated binuclear thioporphyrazine-enhancing photocatalytic performance by expansion of a π-electron system

A novel planar binuclear zinc hexa(2,3-bis(butylthio)) porphyrazine sharing one benzene ring was successfully synthesized, which exhibits superior photocatalytic activity compared to that of its mononuclear counterpart owing to the expansion of the π-electron system.

Modulation of valence band maximum edge and photocatalytic activity of BiOX by incorporation of halides

To better know the photocatalytic performance of bismuth oxyhalides (BiOX, X = Cl, Br, I) regulated by incorporation of halides within nanostructures, BiOX nanosheets were synthesized through morphology controllable solvothermal method and characterized systematically. The organic structural property greatly influences the photocatalytic activity of BiOX: 1) as for neutral molecular phenol, BiOX shows photocatalytic activity in the order of BiOCl > BiOBr > BiOI under simulated sun light irradiation, and the photo-oxidation kinetics follow Eley-Rideal mechanism; and 2) for adsorbed anionic orange II (OII) and cationic methylene blue (MB), BiOX shows photocatalytic activity in the order of BiOCl > BiOBr > BiOI, and the photo-oxidation kinetics follow Langmuir-Hinshelwood mechanism. The crystal structure of the catalyst also greatly influences the photocatalytic activity of BiOX: 1) The relative photo-oxidation power of O₂^•- radicals or HO radicals involved in this study were different which were quantitatively detected using typical radical trapping agent, separately; 2) The relative oxidation power of photogenerated holes (h⁺) in this study were in the order of BiOCl > BiOBr > BiOI, which may be ascribed to lowering the valence band maximum edge of BiOX through incorporation of halides as the atomic number of halides decreased. This study provides novel explanation for fabricating BiOX heterojunctions with tunable photocatalytic reactivity via regulating the halides ratio.

Synthesis and coordination studies of 5-(4′-carboxyphenyl)-10,15,20-tris(pentafluorophenyl)porphyrin and its pyrrolidine-fused chlorin derivative

An efficient strategy was developed to obtain carboxyphenyl porphyrin, chlorins and metal complexes, with potential applications in photonics and biology.

pH-Dependent Assembly of Porphyrin-Silica Nanocomposites and Their Application in Targeted Photodynamic Therapy

Structurally controlled nanoparticles, such as core-shell nanocomposite particles by combining two or more compositions, possess enhanced or new functionalities that benefited from the synergistic coupling of the two components. Here we report new nanocomposite particles with self-assembled porphyrin arrays as the core surrounded by amorphous silica as the shell. The synthesis of such nanocomposite nanoparticles was conducted through a combined surfactant micelle confined self-assembly and silicate sol-gel process using optically active porphyrin as a functional building block. Depending on kinetic conditions, these particles exhibit structure and function at multiple length scales and locations. At the molecular scale, the porphyrins as the building blocks provide well-defined macromolecular structures for noncovalent self-assembly and unique chemistry for high-yield generation of singlet oxygen for photodynamic therapy (PDT). On the nanoscale, controlled noncovalent interactions of the porphyrin building block result in an extensive self-assembled porphyrin network that enables efficient energy transfer and impressive fluorescence for cell labeling, evidenced by absorption and photoluminescence spectra. Finally, the thin silicate shell on the nanoparticle surface allows easy functionalization, and the resultant targeting porphyrin-silica nanocomposites can selectively destroy tumor cells upon receiving light irradiation.