Large Π-conjugated System Research Articles

Self-assembled Quinacridone (QA) based polymers with strong hydrogen bonding for OFETs

For totally disordered organic polymer films, charge mobility is low, while the mobility significantly increases if the polymer exhibits self-assembling properties that can be exploited to generate ordered structures. Introducing a hydrogen-bonding functionality in the materials, resulting in hydrogen-bonded material superstructures, can be a suitable method to fulfil those critical requirements. To the best of our knowledge, the chromophores with hydrogen bonding ability are rarely investigated. Quinacridone (QA) with large π-conjugation system, planar structure as well as the amide and carbonyl groups, is attracted our attention. The hydrogen bonding association (NH…OC) can be formed between the amide groups and the carbonyl units from the QA core. In this work, the QA chromophore is, for the first time, introduced as the electron withdrawing unit in donor-acceptor type polymers for semiconductors. The hydrogen bonded polymers exhibit significantly large red shifted up to 192 nm, which indicates that the hydrogen bonding association in the QA system is powerful. In addition, the hydrogen bonding association led to the polymers not only from a disorder state and inferior crystallinity transferring into a more ordered structures with a block- or fiber-liked-shaped crystalline, but also a strong aggregation. This observation is beneficial for the hole transporting between the neighboring molecules. In addition, the HOMO energy levels have been improved after the hydrogen bonding association formation, which is advantage for the Ohmic contact formation. As a consequent, the hole transport mobility is significantly improved from 0.13 cm2 V−1 s−1–1.02 cm2 V−1 s−1. This work demonstrate that QA is a novel and promising electron-deficient building block with potential strong hydrogen bonding association for the high-performance semiconductor.

Extended Conjugation Strategy Enabling Red-Shifted and Efficient Emission of Orange-Red Thermally Activated Delayed Fluorescence Materials.

In account of the energy gap law, the development of efficient narrow-band gap thermally activated delayed fluorescence (TADF) materials remains a major challenge for the application of organic light-emitting diodes (OLEDs). The orange-red TADF materials are commonly designed with either large π-conjugated systems or strong intramolecular donor-acceptor (D-A) interactions for red-shift emission and small singlet-triplet energy gap (ΔEST). There are rare reports on the simultaneous incorporation of these two strategies on the same material systems. Herein, two orange-red emitters named 1P2D-BP and 2P2D-DQ have been designed by extending the conjugation degree of the center acceptor DQ and increasing the number distribution of the peripheral donor PXZ units, respectively. The emission peak of 1P2D-BP is red-shifted to 615 nm compared to 580 nm for 2P2D-DQ, revealing the pronounced effect of the conjugation extension on the emission band gap. In addition, the distorted molecular structure yields a small ΔEST of 0.02 eV, favoring the acquisition of a high exciton utilization through an efficient reverse intersystem crossing process. As a result, orange-red OLEDs with both 1P2D-BP and 2P2D-DQ have achieved an external quantum efficiency (EQE) of more than 17%. In addition, the efficient white OLED based on 1P2D-BP is realized through precise exciton assignment and energy transport modulation, showing an EQE of 23.6% and a color rendering index of 82. The present work provides an important reference for the design of high-efficiency narrow-band gap materials in the field of solid-state lighting.

Fabrication of p-n Heterostructured Photocatalysts with Triazine-Based Covalent Organic Framework and CuInS2 for High-Efficiency CO2 Reduction.

The application of covalent organic frameworks (COFs) for the photocatalytic reduction of CO2 is mostly limited by severe charge recombination and low sunlight utilization. Herein, a triazine-based COF with an electron-rich and large π-conjugated system (TCOF) was employed as a building block and integrated with CuInS2 (CIS) to construct a noble-metal-free and high-efficiency photocatalyst for CO2 reduction. The in situ growth of CIS nanosheets on TCOF creates a p-n heterojunction, named CIS@TCOF. Compared with TCOF, the CIS@TCOF heterostructure exhibits a dramatically boosted photocatalytic performance in the reduction of CO2. The produced HCOOH yield over 10 wt % CIS@TCOF can be up to 171.2 μmol g-1 h-1 under visible light irradiation with good reproducibility, which is about 3 times as high as that over TCOF. Further in-depth studies indicate that the introduction of CIS not only enhances the visible light utilization but also restrains the recombination of photogenerated electron-hole pairs efficiently and facilitates the photoinduced charge transfer via the p-n heterojunction system due to the unique structural and compositional features. This research shows the great potential of COFs as efficient photocatalytic carbon fixation materials and provides a versatile route to construct semiconductor-COF heterostructures for photocatalysis.

Constructing a Stable Conductive Network for High-Performance Silicon-Based Anode in Lithium-Ion Batteries.

The application of carbon nanotubes to silicon nanoparticles has been used to improve the electrical conductivity of silicon-carbon anodes and prevent agglomeration of silicon nanoparticles during cycling. In this study, the composites are synthesized through an uncomplicated technique that involves the ultrasonication mixing of pyrene derivatives and carbon nanotubes and the formation of complexes with silicon nanoparticles in ultrasonic dispersion and magnetic stirring and then treated under vacuum. When the prepared composites are applied as lithium-ion battery anodes, the Si@(POH-AOCNTs) electrode displays a high reversible capacity of 3254.7 mAh g-1 at a current density of 0.1 A g-1. Furthermore, it exhibits excellent cycling stability with a specific capacity of 1195.8 mAh g-1 after 500 cycles at 1.0 A g-1. The superior electrochemical performance may be attributed to a large π-conjugated electron system of pyrene derivatives, which prompts the formation of a homogeneous CNTs conductive network and ensures the effective electron transfer, while the interaction between hydroxyl functional groups of hydroxypyrene and binder synergizes with CNTs network to further enhance the cycling stability of the composite.

Recent advances in carbon dots-based chromatographic separation materials

Chromatographic column is the core of chromatographic separation, and chromatographic separation material is considered the soul of the chromatographic column. The type and characteristics of the chromatographic separation material directly determine the separation mode and performance of chromatographic columns. The development and preparation of separation materials with novel structures and good separation performance is an ongoing hotspot in chromatography research. Given rapid developments in nanoscience and technology, nanomaterials with unique surface functional groups and large specific surface areas have attracted extensive attention and great interest from researchers in the field of separation science. Carbon dots (CDs), a new type of zero-dimensional fluorescent carbon nanomaterials, have been widely used in bioimaging, light-emitting diodes, sensing, catalysis, drug delivery, and other applications since they were first reported in 2004. These nanomaterials present several advantages over other types of separation materials, including a simple preparation process, low toxicity, easy functionalization, excellent biocompatibility, and photobleaching resistance. In addition, compared with traditional carbon nanomaterials such as graphene and carbon nanotubes, CDs have abundant surface functional groups, nanoscale sizes, and moderate adsorption properties. Hence, when CDs-based new materials are applied as a stationary phase for column chromatography, they can provide rich reaction sites and ensure the uniformity of the chromatographic packing process. The use of CDs can effectively avoid the peak-tailing phenomenon caused by the strong interaction of large π-conjugated systems with some analytes and improve the efficiency of the chromatographic column. As such, these nanomaterials show good application prospects in the field of chromatographic separation. In this review, the development history, classification, and synthesis strategies of CDs are briefly described. We then focus on the development of CDs-based chromatographic separation materials by systematically reviewing the recent advances in the use of CDs-based materials as a stationary phase for high-performance liquid chromatography (including hydrophilic interaction, reversed-phase, mixed-mode, and chiral chromatography), gas chromatography, and capillary electrochromatography, with special emphasis on the preparation methods and applications of various stationary phases. Finally, the development prospects of CDs and future research efforts on these materials are also analyzed and discussed. This review can provide guidance on the rational design and application of new CDs-based chromatographic separation materials.

Modulating Charge Transfer Pathways to Enhance Photocatalytic Performance of the Metal-Organic Layer Nanosheet.

Two-dimensional metal-organic layer (MOL) nanosheets, as nonhomogeneous catalysts, show better optical activity in the field of photocatalysis due to their unique structural advantages. Current research focuses on how to modify the structure of 2D nanosheets by means of crystal engineering to modulate the intralayer electron transfer pathway and systematically investigate the impacts of size effect and electron transfer pathway on the energy utilization efficiency of crystalline materials. In the present work, a triple lophine-derived ligand was designed and prepared, which exhibits a large π-conjugation system and multiple D-A (D: donor, A: acceptor) electron transfer pathways. 2D MOL constructed with Cd ions can be exfoliated by physical sonication to obtain double-walled 2D MOL nanosheets. Compared with the bulk crystalline material, the 2D nanosheets exhibit better photovoltaic properties. Benefiting from the excellent structural advantages, 2D MOL nanosheets could be used as photocatalysts for a variety of aerobic oxidation reactions under mild conditions (10 W white LED, room temperature), such as the trifluoromethylation of coumarins, the synthesis of benzimidazole derivatives from aromatic diamines and aromatic aldehydes, and the preparation of 2,4,6-triarylpyridine derivatives, all with high conversion rates and selectivity (yield typically greater than 88%). The related results illustrate that the introduction of the photoactive triple-lophine unit into 2D MOL nanosheets can effectively modulate the electron transport mode and enhance energy utilization, which provides a new research idea for the development of nonhomogeneous photocatalysts aimed at the applications of visible light-driven organic conversion.

Effect of Surface Chemistry on Macrocycle and Conducting Polymer Based-Carbon Composites

Redox-active carbon composite-based electrodes, especially nitrogen-based redox active materials, can provide high power and energy storage in electrochemical capacitors. These materials include porphyrin macrocycles which are found in nature and possess unique electronic and redox-active properties from their large π-conjugated systems [1], [2]. When compositing with carbon-based materials such as carbon nanotubes (CNTs), they have shown increased stability and long-term performance. Previous work using macrocyclic tetraphenyl porphyrin sulfonate (TPPS) in CNT-based composites demonstrated improved capacitive profiles, better interfacial kinetics, and charge retention introduced in capacitive electrodes [3], [4]. On the other hand, conducting polymers with π-conjugated backbones also enabled high charge storage when used in composites [5]. To further advance these capabilities, the effects and mechanisms of surface functionalities of carbon substrates need to be investigated. For example, the presence of carboxyl groups on CNTs has been shown to improve charge storage through favourable interfacial interactions in some conducting polymers [6], [7]. The challenge as highlighted in Figure 1 lies in understanding which redox-active species, e.g. macrocycle or conducting polymer, will favour certain surface functionalities based on the nature of their interactions. Thus, a systematic investigation to design and create desirable composites and interactions for high energy and power densities, and to extend to low-cost carbon sources including waste biomass-based activated carbons.In this work, we conducted a systematic study comparing the effect of several surface functionalities like carboxyl groups on TPPS macrocycles and on conducting polymer-based carbon composites to answer the question on why certain surface functionalities are favored for each species. Preliminary studies have shown presence of TPPS has increased the capacitive profiles, reaction kinetics and rate capabilities of CNT composites, exceeding the conducting polymer counterparts. But this capacitive increase can be further improved through surface modification. This study leveraged layer-by-layer deposition approaches to fabricate redox-active carbon composites, followed by electrochemical characterizations using cyclic voltammetry and electrochemical impedance spectroscopy. Surface morphology was studied using electron microscopy while surface functional groups were investigated using x-ray photoelectron spectroscopy. The findings from this study can be used to implement systematic surface modification for redox-active carbon composites to improve energy storage, towards a more sustainable future.

Two Birds One Stone: Graphene Assisted Reaction Kinetics and Ionic Conductivity in Phthalocyanine-Based Covalent Organic Framework Anodes for Lithium-ion Batteries.

This work reports a covalent organic framework composite structure (PMDA-NiPc-G), incorporating multiple-active carbonyls and graphene on the basis of the combination of phthalocyanine (NiPc(NH2 )4 ) containing a large π-conjugated system and pyromellitic dianhydride (PMDA) as the anode of lithium-ion batteries. Meanwhile, graphene is used as a dispersion medium to reduce the accumulation of bulk covalent organic frameworks (COFs) to obtain COFs with small-volume and few-layers, shortening the ion migration path and improving the diffusion rate of lithium ions in the two dimensional (2D) grid layered structure. PMDA-NiPc-G showed a lithium-ion diffusion coefficient (DLi + ) of 3.04 × 10-10 cm2 s-1 which is 3.6 times to that of its bulk form (0.84 × 10-10 cm2 s-1 ). Remarkably, this enables a large reversible capacity of 1290 mAhg-1 can be achieved after 300 cycles and almost no capacity fading in the next 300 cycles at 100mAg-1 . At a high areal capacity loading of ≈3 mAhcm-2 , full batteries assembled with LiNi0.8 Co0.1 Mn0.1 O2 (NCM-811) and LiFePO4 (LFP) cathodes showed 60.2% and 74.7% capacity retention at 1 C for 200 cycles. Astonishingly, the PMDA-NiPc-G/NCM-811 full battery exhibits ≈100% capacity retention after cycling at 0.2 C. Aided by the analysis of kinetic behavior of lithium storage and theoretical calculations, the capacity-enhancing mechanism and lithium storage mechanism of covalent organic frameworks are revealed. This work may lead to more research on designable, multifunctional COFs for electrochemical energy storage.

Multifunctional broadband visible-light absorbing selenophene modified bodipy photosensitizers

Large π-conjugated organic systems with effective photosensitization are highly desirable for many photochemical applications. Herein, a series of π-conjugated selenophene-substituted boron dipyrromethene (known as bodipy) dyes (MB-Se, 2B–Se, MB-Se-2Br) were prepared by appending selenophene electron-donor to the core of bodipy acceptors via alkynyl bridge and their excited state properties were investigated. Optical spectroscopy revealed that although these three selenophene-substituted bodipy dyes have nearly identical molecular profiles, their photophysical properties and excited state dynamics are drastically different. Higher triplet quantum efficiency (ΦΔ = 82%) was observed for MB-Se, derivative in which α,β-positions of bodipy decorated with methyl substituents, compared to another dye 2B–Se, which showed inefficient triplet population (ΦΔ = 25%). Employing steady-state absorption and emission spectroscopies, we demonstrated that the designed selenophene-substituted bodipy dyes has excellent J-aggregation capabilities. Notably, the J-aggregates of selenophene-substituted bodipy dyes display NIR emission. The potential of devised selenophene-substituted bodipy dyes in triplet fusion upconversion was also demonstrated; a blue upconverted emission was realized upon irradiating the mixture of bodipy dyes and TIPS-AC acceptor with 589 nm CW-laser. The selenophene-substituted bodipy dyes were also confirmed to be a potent photodynamic therapeutic reagent; with an IC50 value of 0.76 μM, nearly 6 times lower than that of the iodide-appended bodipy photosensitizer (BDP-2I, 6.0 μM). This study hopes to provide valuable guidelines for the future development of multipurpose triplet photosensitizers.

Luminescent Lanthanide Complexes for Effective Oxygen-Sensing and Singlet Oxygen Generation.

Oxygen quantification using luminescence has attracted considerable attention in various fields, including environmental monitoring and clinical analysis. Among the reported luminophores, trivalent lanthanide complexes have displayed characteristic narrow emission bands with high brightness. This bright emission is based on photo-sensitized energy transfer via organic triplet states. The organic triplet states in lanthanide complexes effectively react with the triplet oxygen, enabling oxygen quantification by lanthanide luminescence. Some TbIII and EuIII complexes with slow deactivation processes have also formed the excited state equilibrium, thus resulting in the emission-lifetime based oxygen sensing property. The combination of TbIII /EuIII emission, EuIII /SmIII emission, EuIII /ligand phosphorescence, and ligand fluorescence/ligand phosphorescence provide the ratiometric oxygen-sensing properties. Moreover, the reaction generates singlet oxygen species which exhibit numerous applications in the photo-medical field. The ligands with large π-conjugated aromatic systems, such as porphyrin, phthalocyanine, and polyaromatic compounds, induces highly efficient oxygen generation. The combination of effective luminescence with singlet-oxygen generation by the lanthanide complexes render them suitable for photo-driven theranostics. This review summarizes the research progress of lanthanide complexes with efficient oxygen-sensing and singlet-oxygen generation properties.

Rapid charge transfer in covalent organic framework via through-bond for enhanced photocatalytic CO2 reduction

Charge transfer efficiency between discrete photosensitizers and catalytic sites is a key limiting factor in artificial photosynthesis. It is highly desirable but challenging to efficiently combine the two sections into an integration system and get insight into the kinetics and mechanisms. Here in, the photosensitizer [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) and active cobalt porphyrin (Co-Por) sites were integrated into a covalent organic framework (COF), named COF-RuBpy-Co, for efficient charge transfer and photocatalytic CO2 reduction. The catalyst COF-RuBpy-Co exhibited excellent CO2 photoreduction activity towards CO production with a rate of 547 μmol g−1h−1, which is 1.4-fold enhancement over the physical mixture of Ru(bpy)3Cl2 and COF-Bpy-Co. In situ X-ray photoelectron spectroscopy combined with theoretical calculation results revealed that COF-RuBpy-Co achieved efficient photoelectron transfer from [Ru(bpy)3]2+ to cobalt porphyrin. More importantly, transient absorption spectroscopy indicated that the covalent linking [Ru(bpy)3]2+and Co-Por units realized a faster charge transfer (44.2 ps) over the large π-conjugated system. This work provides vital insights into the charge carrier transfer process and demonstrates the potential of COFs as a platform in artificial photosynthesis.

Visible light activated energy storage in solid-state Azo-BF2 switches.

We present here a group of Azo-BF2 photoswitches that store and release energy in response to visible light irradiation. Unmodified Azo-BF2 switches have a planar structure with a large π-conjugation system, which hinders E-Z isomerization when in a compacted state. To address this challenge, we modified the switches with one or two aliphatic groups, which altered the intermolecular interactions and arrangement of the photochromes in the solid state. The derivative with two substituents exhibited a non-planar configuration that provided particularly large conformational freedom, allowing for efficient isomerization in the solid phase. Our discovery highlights the potential of using double aliphatic functionalization as a promising approach to facilitate solid-state switching of large aromatic photoswitches. This finding opens up new possibilities for exploring various photoswitch candidates for molecular solar thermal energy storage applications.

Anthracene-Fused Oligo-BODIPYs: A New Class of π-Extended NIR-Absorbing Materials.

Large π-conjugated systems are key in the area of molecular materials. Herein, we prepare via AuI -catalyzed cyclization a series of fully π-conjugated anthracene-fused oligo-BODIPYs. Their structural and optoelectronic properties were studied by several techniques, ranging from X-ray, UV/Vis, and cyclic voltammetry to transient absorption spectroscopy. As a complement, their electronic structures were explored by means of Density Functional Theory (DFT) calculations. Depending on the size and shape of the π-conjugated skeleton, unique features-such as face-to-face supramolecular organization, NIR absorption and fluorescence as well as strong electron accepting character-were noted. All in all, the aforementioned features render them valuable for technological applications.

Organic Zinc-Ion Battery: Planar, π-Conjugated Quinone-Based Polymer Endows Ultrafast Ion Diffusion Kinetics.

A novel poly(phenazine-alt-pyromellitic anhydride) (PPPA) has been successfully designed and synthesized via a condensation polymerization strategy as promising cathode material in organic zinc-ion batteries. Electrochemical quartz crystal microbalance (EQCM), FTIR and XPS characterizations verify a reversible Zn2+ -coordination mechanism in our PPPA cathode. Intriguingly, an ultrahigh Zn2+ diffusion coefficient of 1.2×10-7 cm2 s-1 was found in this large π-conjugated system, which is the highest one among all organic cathode materials for zinc-ion batteries. Theoretical calculations reveal the extended π-conjugated plane in our PPPA sample results in a significant reduction on energy gap, effectively accelerating intramolecular electron transfer during charge/discharge process. Our finding provides insights to achieve high zinc-ion transport kinetics by a design strategy on planar polymer system.

Multiple stimuli-responsive electropolymerized polymer based on quinacridone dye via breaking conjugated structure strategy

Quinacridone (QA) dye shows great potential applications in organic optoelectronics owing to the large π-conjugated system, good photothermal stability, and high charge carrier transport behavior. In this work, two quinacridone-based monomers QA-B-CZ and QA-6C-CZ were designed and synthesized, and their polymers pQA-B-CZ and pQA-6C-CZ were prepared by electrochemical polymerization. Both pQA-B-CZ and pQA-6C-CZ exhibit multicolored electrochromic properties at different potentials. It is more intriguing that the pQA-6C-CZ bearing with the flexible long alkyl chain preserves multiple stimuli-responsive characteristics compared to pQA-B-CZ containing benzene unit. pQA-6C-CZ film exhibits reversible and robust acidichromic behavior switched from the initial pink color to purple color, implying its potential as a hydrochloric acid sensor. Besides, pQA-6C-CZ presents reversible orange fluorescence and it disappears in response to electric-/acid-stimulation. The multiple stimuli-responsive behaviors should be ascribed to that the flexible long alkyl chains break the conjugated structure between QA and carbazole, which is beneficial for developing their inherent characters, respectively. The work puts forward a new design strategy for the preparation of multifunctional optoelectronic materials based on QA dye.

Recent advancements of photo- and electro-active hydrogen-bonded organic frameworks

The development of hydrogen-bonded organic frameworks (HOFs) with predictable topologies and robust structures for targeted functionality was initially hindered by the relatively weak H-bonding interactions as many HOFs would collapse upon guest solvent removal. Recently, the design of tectons with large π-conjugated systems that form intermolecular shape-fitted π–π stacking interactions has proven to be an effective strategy to create chemically and thermally stable HOFs. More importantly, these HOFs with large π-conjugated tectons exhibit accelerated redox hopping processes due to more favorable through-space orbital overlap interactions. These intrinsic photoelectric properties render HOFs an appealing and unique class of photoactive and electroactive porous materials for catalysis, sensing, and biomedical applications. Based on shape-fitted π–π stacking strategy, various robust photoactive and electroactive HOFs have been built from tectons containing both photosensitive or redox-active organic cores and hydrogen bonding sites. This review summarizes the recent advancements, including synthetic methods and diverse applications, in the development of photo- and electro-active HOFs. Considering the numerous photo- and electro-active organic units available, as well as the virtually unlimited potential combinations of organic cores and hydrogen bonding sites, we anticipate that this review will inspire scientists in a range of disciplines, ranging from porous materials to organic photoelectric materials and catalysis scientists, to further explore functional photo- and electro-active HOF materials.

Two-Photon-Near Infrared-II Antimicrobial Graphene-Nanoagent for Ultraviolet-Near Infrared Imaging and Photoinactivation.

Nitrogen doping and amino group functionalization through chemical modification lead to strong electron donation. Applying these processes to a large π-conjugated system of graphene quantum dot (GQD)-based materials as electron donors increases the charge transfer efficiency of nitrogen-doped amino acid-functionalized GQDs (amino-N-GQDs), resulting in enhanced two-photon absorption, post-two-photon excitation (TPE) stability, TPE cross-sections, and two-photon luminescence through the radiative pathway when the lifetime decreases and the quantum yield increases. Additionally, it leads to the generation of reactive oxygen species through two-photon photodynamic therapy (PDT). The sorted amino-N-GQDs prepared in this study exhibited excitation-wavelength-independent two-photon luminescence in the near-infrared region through TPE in the near-infrared-II region. The increase in size resulted in size-dependent photochemical and electrochemical efficacy, increased photoluminescence quantum yield, and efficient two-photon PDT. Therefore, the sorted amino-N-GQDs can be applicable as two-photon contrast probes to track and localize analytes in in-depth two-photon imaging executed in a biological environment along with two-photon PDT to eliminate infectious or multidrug-resistant microbes.

Graphene near infrared-I/II probe in two-photon excitation-wavelength-independent photoluminescence and photoinactivation

Nitrogen doping and amino-group functionalization through chemical modification can engender enhance electron donation. Using a homemade femtosecond titanium:sapphire laser optical system operated at a low energy and short photoexcitation time [power: 200.0 nJ pixel−1; scanning frequency: 150 scans (∼0.80–1.33 s); excitation wavelength: 870, 910, or 970 nm], this study conducted these processes on the large π-conjugated system of graphene quantum dot (GQD)-based materials functioning as electron donors; this improved the efficiency of charge transfer to the prepared amino-N-GQDs, resulting in enhanced two-photon absorption, excitation-wavelength-independent photoluminescence (EWI-PL), radiative efficiency, excitation absolute cross section, and excitation from the near-infrared (NIR)-I to the NIR-II region. The lifetime decreased and quantum yield (QY) increased. The sorted amino-N-GQDs exhibited two-photon EWI-PL emissions between the ultraviolet and NIR-I regions, leading to the generation of reactive oxygen species (ROS), which functioned as two-photon photosensitizers for photodynamic therapy (PDT). Increasing the mean lateral size of the particles increased the N-functionality-dependent photochemical and electrochemical activities, which improved the PL QY and thus enhanced the efficiency of two-photon PDT. Additionally, a polystyrene sulfonate (PSS) coating was applied (forming sorted amino-N-GQD-PSS); the sulfur atoms introduced by the PSS induced the radiative recombination of localized electron–hole pairs and then improved the sorted amino-N-GQD surfaces by strengthening the quantum confinement of their emissive energy. Thus, compared with the sorted amino-N-GQDs that were not coated, the PSS-coated materials had superior two-photon properties. No ROS were detected. Accordingly, these materials are suitable for use as two-photon contrast probes for analyte tracking and localization.

Conjugated Porphyrin Materials for Solar Fuel Generation

Abstract: Conjugated materials have emerged as a new class of photocatalysts for solar fuel generation, thus allowing for the Sun’s energy to be converted into a storable fuel that can be used without further emissions at the point of use. Many different building blocks have been used to make conjugated materials that act as photocatalysts allowing for efficient light absorption and tuing of photophysical properties. The porphyrin moiety is a very interesting building block for photocatalysts as the large π-conjugated system allows efficient light absorption. Metalation of porphyrins allows for further tuning of the materials’ properties, thus further expanding the property space that these materials can cover. This allows to design and better control over the properties of the materials, which is discussed in this review together with the state-of-the-art in porphyrin photocatalysts and hybrid systems.

High-performance electrochromic supercapacitor based on quinacridone dye with good specific capacitance, fast switching time and robust stability

• QA dyes were designed and firstly prepared into electrochromic polymers. • The polymers with three donor units show different electrochemical behaviors. • pC10QA-2EDOT film exhibits remarkable electrochromic properties. • The device based on pC10QA-2EDOT exhibits robust cyclic stability. • The electrochromic supercapacitor can make a LED light for more than 85 s. Quinacridone (QA) dye with large π-conjugation system exhibit excellent optical, thermal and chemical properties. A series of QA derivatives (C10QA-2T, C10QA-2EDOT, C10QA-2DT) were designed and synthesized with different donor units (including thiophene, EDOT and bithiophene) in this work. Three monomers show different HOMO energy levels and onset oxidation potentials. Their corresponding polymer films were obtained by electrochemical polymerization. Compared to pC10QA-2T and pC10QA-2DT, pC10QA-2EDOT exhibits better integrated electrochromic properties in terms of multicolor showing (yellow, gray and blue), higher optical contrast (more than 40% in the visible region), larger coloration efficiency (498 cm 2 /C at 455 nm), faster switching time (less than 1 s) and better cyclic stability. It is intriguing that the electrochromic device based on pC10QA-2EDOT exhibits robust stability over 50,000 cycles with almost no decay of its original optical contrast. In addition, pC10QA-2EDOT film possesses large volume specific capacitance of up to 322 F/cm 3 , which should be ascribed to that the loose and porous structures owing to large dihedral angles caused by the steric hindrance of oxygen on the EDOT may facilitate the ion diffusion during the doping/dedoping process. Hence, the electrochromic supercapacitor can supply power to a green LED for 85 s. This work pioneers QA dye in the electrochromic field and further develops a new electrochromic energy storage device with visual color display, which may have potential prospects in portable and wearable electronic devices.