Porphyrin–BODIPY-based hybrid model compounds for artificial photosynthetic reaction centers

In this review, we report the synthesis and photophysical studies of porphyrin–4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) compounds linked either with different covalent bonds or with axial coordination to metalloporphyrin. BODIPY moiety significantly increases the light absorption capability of porphyrins by efficient BODIPY to porphyrin excitation energy transfer. The type of linkage between the two chromophores significantly affects the energy transfer efficiency. The most efficient energy transfer was proved for compounds linked via a cyanuric chloride bridge (∼99% quenching). Therefore, this type of bond seems to be more appropriate choice in constructing porphyrin–BODIPY assemblies for light harvesting applications. Moreover, the functionalization of the conjugates with fullerenes appears to be interesting electron transfer dynamics in the excited state.     

Toward the most versatile fluorophore: Direct functionalization of BODIPY dyes via regioselective C—H bond activation

BODIPY dyes are privileged fluorophores that are now widely used in highly diverse research fields. An overview of BODIPY dyes and a summarization of the different synthetic methodologies reported for direct C-H functionalization of the BODIPY framework have been provided.     

Toward the most versatile fluorophore: Direct functionalization of BODIPY dyes via regioselective C–H bond activation

Fluorescent dyes are heavily sought for their potentials applications in bioimaging, sensing, theranostic,and optoelectronic materials. Among them, BODIPY dyes are privileged fluorophores that are now widely used in highly diverse research fields. The increasing success of BODIPY dyes is closely associated with their excellent and tunable photophysical properties due to their rich functionalization chemistry.Recently, growing research efforts have been devoted to the direct functionalization of the BODIPY core,because it allows the facile installation of desired functional groups in a single atom economical step. The challenges of this direct C–H derivation come from the difficulties in finding suitable functionalization agents and proper control of the regioselectivity of the functionalization. The aim of this work is to provide an overview of BODIPY dyes and a summarization of the different synthetic methodologies reported for direct C–H functionalization of the BODIPY framework.     

Near-Infrared (>1000 nm) Light-Harvesters: Design,Synthesis and Applications

Organic molecules can absorb or emit light in UV, visible and infra-red (IR) region of solar radiation. Fifty percent of energy of solar radiation lies in the IR region of solar spectrum and extended π-conjugated molecules containing low optical band gap can absorb NIR radiations. Recently IR molecules have grabbed the attention of synthetic chemists. Although only few molecules have been reported so far such as derivative of BODIPY, naphthalimide, porphyrins, perylene, BBT etc., they have shown highest absorbing capacity towards greater than 1100 nm. These compounds have potential applications in different fields, such as for biomedical and optoelectronic applications. In this review, we present different classes of light-harvesters with harvesting range above 1000 nm.     

Pairing of α-Fused BODIPY: Towards Panchromatic n-Type Semiconducting Materials

A chemical strategy to efficiently perform the dimerization of α-fused boron-dipyrromethene (BODIPY) is reported. The straightforward synthesis of one of these dimers is described and its properties have been investigated through UV/Vis spectroscopy, cyclic voltammetry, differential scanning calorimetry, and charge-carrier mobility measurements by using organic field-effect transistors and space–charge-limited current diodes. The results allow a chemical strategy to decrease the tendency of α-fused BODIPY to crystallize, to increase its light-harvesting properties, and to promote isotropic charge carriers transport. Moreover, the disclosed approach is also a way to maintain the deep LUMO level of α-fused BODIPY; thus making this class of materials highly desirable for optoelectronic applications.     

Structural modification of BODIPY: Improve its applicability

The synthesis of biocompatibility and tissue penetrating BODIPY dyes have been summarized.     

Antimonene: From Experimental Preparation to Practical Application

The two‐dimensional material antimonene was first reported in 2015. Subsequently, its unique properties, including enhanced stability, high carrier mobility, and band‐gap tunability, were predicted theoretically. These theoretical results have motivated experimental confirmation and thus a better understanding of this new material. Recently, the preparation of antimonene and its attempted use in several applications have attracted extensive attention. This Minireview focuses on both the experimental preparation and practical applications of antimonene, including the results of recent research on novel methods of preparing antimonene and its potential applications in optoelectronic devices, electrocatalysis, energy storage, and cancer therapy. Moreover, it provides insight that could further improve the preparation of antimonene and also describes numerous opportunities for application.     

Ultrafast Photoinduced Charge Separation in Wide‐Band‐Capturing Self‐Assembled Supramolecular Bis(donor styryl)BODIPY–Fullerene Conjugates

A new series of self‐assembled supramolecular donor–acceptor conjugates capable of wide‐band capture, and exhibiting photoinduced charge separation have been designed, synthesized and characterized using various techniques as artificial photosynthetic mimics. The donor host systems comprise of a 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY) containing a crown ether entity at the meso‐position and two styryl entities on the pyrrole rings. The styryl end groups also carried additional donor (triphenylamine or phenothiazine) entities. The acceptor host system was a fulleropyrrolidine comprised of an ethylammonium cation. Owing to the presence of extended conjugation and multiple chromophore entities, the BODIPY host revealed absorbance and emission well into the near‐IR region covering the 300–850 nm spectral range. The donor–acceptor conjugates formed by crown ether–alkyl ammonium cation binding of the host–guest system was characterized by optical absorbance and emission, computational, and electrochemical techniques. Experimentally determined binding constants were in the range of 1–2×10⁵ M ^?1. An energy‐level diagram to visualize different photochemical events was established using redox, computational, absorbance, and emission data. Spectral evidence for the occurrence of photoinduced charge separation in these conjugates was established from femtosecond transient absorption studies. The measured rates indicated ultrafast charge separation and relatively slow charge recombination revealing their usefulness in light‐energy harvesting and optoelectronic device applications. The bis(donor styryl)BODIPY‐derived conjugates populated their triplet excited states during charge recombination.     

Structural modification of BODIPY: Improve its applicability

BODIPY has been considered a potential scaffold because of their neutral total charge, sharp absorption,and emission with high fluorescence quantum yield. However, the drawback of emission wavelength at less than 600 nm and hydrophobicity limit its application. One of the extremely interesting properties of BODIPY is that small modifications to their structures could be able to tune their properties, mainly including the absorption/emission wavelength and the hydrophilicity. This review focuses on the modification at different positions of BODIPY to improve the water-solubility and emission wavelength that describe their spectral, photophysical properties and applicability, which is helpful for the researchers to rationally design BODIPY dyes to adapt a wide range of applications.     

High-contrast flicker luminescence on dynamic covalent structure based nanoaggregates

In nanoscience, molecular switches have played a significant role to deliver different control abilities to practical functions,whereas high-contrast luminescence switchable manipulation at nanoscale is still limited. Since the tuning for emission behavior with high contrast ratio strongly connects to numerous visualized sensing and optoelectronic applications, we here report that autonomous p H control can be enrolled to address a high-contrast molecular emission change at the nanoaggregated level, for gaining a flicker luminescence performance in aqueous media. Employing a BODIPY contained dynamic covalent dye, we find its luminescent signal and nanoaggregate size can be spontaneously adjusted in water. On this basis, high-contrast luminescence switching of the material can be achieved upon the alternate introduction of base and acid into the aggregation state. Such a behavior can be attributed to a p H triggered photo-induced electron transfer regulation process. The dye aggregates can be well endocytosed for bioimaging and its luminescent variation can be autonomously displayed as a flicker effect. These results provide new visions for the design and development of smart materials with a dynamic luminescence behavior.     

Human Serum Albumin Labelling with a New BODIPY Dye Having a Large Stokes Shift

BODIPY dyes are photostable neutral derivatives of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene. These are widely used as chemosensors, laser materials, and molecular probes. At the same time, BODIPY dyes have small or moderate Stokes shifts like most other fluorophores. Large Stokes shifts are preferred for fluorophores because of higher sensitivity of such probes and sensors. The new boron containing BODIPY dye was designed and synthesized. We succeeded to perform an annulation of pyrrole ring with coumarin heterocyclic system and achieved a remarkable difference in absorption and emission maximum of obtained fluorophore up to 100 nm. This BODIPY dye was equipped with linker arm and was functionalized with a maleimide residue specifically reactive towards thiol groups of proteins. BODIPY residue equipped with a suitable targeting protein core can be used as a suitable imaging probe and agent for Boron Neutron Capture Therapy (BNCT). As the most abundant protein with a variety of physiological functions, human serum albumin (HSA) has been used extensively for the delivery and improvement of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare albumin-based multimodal constructions. The released sulfhydryl groups of the homocysteine functional handle in thiolactone modified HSA were labeled with BODIPY dye to prepare a labeled albumin-BODIPY dye conjugate confirmed by MALDI-TOF-MS, UV-vis, and fluorescent emission spectra. Cytotoxicity of the resulting conjugate was investigated. This study is the basis for a novel BODIPY dye-albumin theranostic for BNCT. The results provide further impetus to develop derivatives of HSA for delivery of boron to cancer cells.     

含稠合外环的氟硼荧染料类pH荧光探针的研究

以环己醇为起始原料,首先经过改进的三步法制备出2-乙氧羰基-3,4-四亚甲基吡咯,并用过量氢化铝锂高温还原得到2-甲基-3,4-四亚甲基吡咯;再将其分别与4-二甲氨基苯甲醛、4-羟基苯甲醛、4-甲氧基苯甲醛、苯甲醛、4-醛基苯并冠-5等芳醛衍生物在三氟乙酸的催化作用下发生缩合反应,用2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)氧化并依次用N(Et)3和BF3.OEt2处理后得到5种新型含稠合外环的BODIPY类染料衍生物。研究了它们的吸收和发射光谱,并采用荧光光谱滴定方法研究了它们在CH3OH-H2O(1∶1,V/V)中对pH的响应能力。结果表明:BODIPY 1和2在可见光激发下,可以分别作为酸、碱环境下的pH荧光探针并且这两种荧光探针在荧光"开/关"状态之间的转化可以通过质子化和去质子化的方式调控。另外,还初步探讨了荧光探针的设计原理及传感机制。     

Two π-Electrons Make the Difference: From BODIPY to BODIIM Switchable Fluorescent Dyes

(aza-)BODIPY dyes (boron dipyrromethene dyes) are well-established fluorophores due to their large quantum yields, stability, and diversity, which led to promising applications including imaging techniques, sensors, organic (opto)electronic materials, or biomedical applications. Although the control of the optical properties in (aza-)BODIPY dyes by peripheral functional groups is well studied, we herein present a novel approach to modify the 12 π-electron core of the dipyrromethene scaffold. The replacement of two carbon atoms in the β-position of a BODIPY dye by two nitrogen atoms afforded a 14 π-electron system, which was termed BODIIM (boron diimidazolylmethene) in systematic analogy to the BODIPY dyes. Remarkably, the BODIIM dye was obtained with a BH₂-rigidifying entity, which is currently elusive and highly sought after for the BODIPY dye class. DFT-Calculations confirm the [12+2] π-electron relationship between BODIPY and BODIIM and reveal a strong shape correlation between LUMO in the BODIPY and the HOMO of the BODIIM. The modification of the π-system leads to a dramatic shift of the optical properties, of which the fluorescent emission is most noteworthy and occurs at much larger Stokes shift, that is, ≈500 cm⁻¹ in BODIPY versus >4170 cm⁻¹ in BODIIM system in all solvents investigated. Nucleophilic reactivity was found at the meso-carbon atom in the formation of stable borane adducts with a significant shift of the fluorescent emission, and this behavior contrasts the reactivity of conventional BODIPY systems. In addition, the reverse decomplexation of the borane adducts was demonstrated in reactions with a representative N-heterocyclic carbene to retain the strongly fluorescent BODIIM compound, which suggests applications as fully reversible fluorescent switch.     

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.     

Optical properties and photonic devices of doped carbon nanotubes

Chemical doping of carbon nanotubes provides a variety of opportunities for tailoring the physical properties of carbon nanotubes. In this review, we discussed the optical properties of doped carbon nanotubes and the related applications as nanoscale photonic devices. The fundamental optical properties of carbon nanotubes with various chemical doping have been summarized. Novel optoelectronic and photonic devices based on doped carbon nanotubes, such as optical nonlinear materials, optical limiting devices, photovoltaic devices, etc., have been discussed.     

The Structure‐property Relationships of D‐π‐A BODIPY Dyes for Dye‐sensitized Solar Cells

BODIPY dyes have attracted considerable attention as potential photosensitizers in dye‐sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D‐π‐A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure‐property relationships of D‐π‐A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6‐modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure‐property relationships give valuable information and guidelines for designing new D‐π‐A BODIPY dyes for DSSCs.

     

A‐D‐A Type Small Molecules Based on Boron Dipyrromethene for Solution‐Processed Organic Solar Cells

The unique properties of boron dipyrromethene (BODIPY) dyes including facile synthesis, high absorption coefficients, and delocalized molecular orbitals as well as excellent photochemical and thermal stability, make them promising as materials for organic solar cells. Accordingly, in this study three A‐D ‐A structural small molecules of BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY have been synthesized, in which two BODIPY acceptor units are symmetrically conjugated to 4,8‐bis(5‐(2‐ethylhexyl) thiophen‐2‐yl)benzo[1,2‐b:4,5‐b]dithiophene (BDTT), 9,9‐dioctyl‐9H‐fluorene (FL), and thieno[3,2‐b]thiophene (TT) donor cores, respectively. The manipulation of the structural parameters significantly improves the performances of the BHJ OSCs, which show power conversion efficiencies of 4.75 %, 1.51 %, and 1.67 % based on [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor material and BDTT‐BODIPY, FL‐BODIPY, and TT‐BODIPY as the donor materials, respectively.     

二维半导体材料纳米电子器件和光电器件

近年来,随着各领域对微电子器件集成度及性能要求的不断提高,发展基于二维半导体材料的新型高性能功能性器件成为了突破当前技术瓶颈的重要环节和关键方向。目前,作为新型二维半导体材料的代表,二维过渡金属二硫化物、二维黑磷以及范德瓦尔斯异质结凭借其在电学、热学、机械、光学等方面的优异性能已经成为了发展高性能纳米电子器件和光电器件的最具潜力的材料之一。在本综述中,首先概述了几种用于纳米器件的常见二维材料,分析了材料的结构、性能及其在纳米器件中的应用,其次重点对基于过渡金属二硫化物、黑磷以及由其衍生的范德瓦尔斯异质结的纳米电子器件和光电器件的最新研究进展进行讨论,最后对目前二维半导体纳米器件所面临的挑战以及未来的发展方向进行总结及分析,从而为未来发展高性能功能性纳米器件提供支持。     

Fluorescent indicators based on BODIPY

This critical review covers the advances made using the 4-bora-3a,4a-diaza-s-indacene (BODIPY) scaffold as a fluorophore in the design, synthesis and application of fluorescent indicators for pH, metal ions, anions, biomolecules, reactive oxygen species, reactive nitrogen species, redox potential, chemical reactions and various physical phenomena. The sections of the review describing the criteria for rational design of fluorescent indicators and the mathematical expressions for analyzing spectrophotometric and fluorometric titrations are applicable to all fluorescent probes (206 references).